# Top 30 professional services firms in Istanbul

Tamtam tracks 41 professional services firms headquartered in Istanbul. This list ranks the 30 largest by number of employees on LinkedIn, led by Avukat, Serbest Muhasebeci Mali Müşavirlik Hizmetleri and KUCUKYiLMAZ Consulting Co.. Their median headcount is 414. Half of them were founded in 2006 or later.

These professional services firms in Istanbul span various sectors including law, accounting, IT, and business consulting. The list features both large established firms like KPMG Türkiye, which provides audit, tax, and advisory services, and younger companies such as Avukat, a legal practice founded in 2013. Other notable firms include BGTS, an international technology consulting firm, and KUCUKYiLMAZ Consulting Co., which has 25 years of experience in the friction industry.

A significant pattern observed is the prevalence of IT services and consulting firms, indicating a strong focus on technology within Istanbul's professional services landscape. Companies like OBSS, specializing in cloud-powered future technologies, and adesso Turkey, focused on digital transformation, highlight this trend. All the listed companies are headquartered in Istanbul, consolidating the city's role as a hub for professional services.

🇹🇷 Istanbul · 30 companies · Updated Nov 12, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Avukat](https://www.tamtam.ai/c/avukat) (sanliurfaavukat.com)<br>Explore detailed information about legal services on our page | Law Practice | 🇹🇷 Istanbul | 4,336 | 2013 |
| 2 | [Serbest Muhasebeci Mali Müşavirlik Hizmetleri](https://www.tamtam.ai/c/serbest-muhasebeci-mali-musavirlik-hizmetleri) (smmmemrahkucukdeniz.com)<br>An accounting office in Istanbul providing practical solutions to tax issues for clients nationwide, focusing on communication, trust, and quality service | Accounting | 🇹🇷 Istanbul | 3,332 | 2013 |
| 3 | [KUCUKYiLMAZ Consulting Co.](https://www.tamtam.ai/c/kucukyilmaz-consulting-co) (facebook.com)<br>With 25 years of experience in the friction industry, offering assistance in compounding, process, product, and business development, representing major suppliers | Motor Vehicle Manufacturing | 🇹🇷 Istanbul | 2,363 | 2004 |
| 4 | [KPMG Türkiye](https://www.tamtam.ai/c/kpmg-turkiye) (kpmg.com)<br>Providing audit, tax, and advisory services to diverse industries with a sector-focused approach and extensive local and international expertise. | Business Consulting and Services | 🇹🇷 Istanbul | 1,446 | 1982 |
| 5 | [BGTS](https://www.tamtam.ai/c/bgts) (bilgeadam.com)<br>An international technology consulting firm specializing in software development, IT consulting, business processes, QA & testing, big data, cloud, AI/ML, and cybersecurity services | IT Services and IT Consulting | 🇹🇷 Istanbul | 1,182 | 1997 |
| 6 | [OBSS](https://www.tamtam.ai/c/obss) (obss.tech)<br>Leader in technology consulting for a cloud-powered future, with expertise in banking, insurance, e-commerce, retail, and start-ups Strong team with offices in Europe | IT Services and IT Consulting | 🇹🇷 Istanbul | 870 | 2005 |
| 7 | [Özel bir danışmanlık şirketi](https://www.tamtam.ai/c/ozel-bir-dan-smanl-k-sirketi) (kml.com.tr)<br>Strategic planning, brand management, marketing, sales management, R&D, innovation, HR, supply chain, quality management, IT, corporate governance, digital transformation, corporate training | Business Consulting and Services | 🇹🇷 Istanbul | 705 | 2019 |
| 8 | [DIP](https://www.tamtam.ai/c/dip) (dip.com)<br>Specializing in Data & Analytics solutions, creating custom solutions for organizations, providing consulting services in data transformation, analysis, and management processes | IT Services and IT Consulting | 🇹🇷 Istanbul | 702 | 2012 |
| 9 | [adesso Turkey](https://www.tamtam.ai/c/adesso-turkey) (adesso.com.tr)<br>A digital transformation company with agile beliefs, employing over 10,000 people worldwide, offering custom software development and IT solutions | IT Services and IT Consulting | 🇹🇷 Istanbul | 628 | 2013 |
| 10 | [Commencis](https://www.tamtam.ai/c/commencis) (commencis.com)<br>A company specializing in experience design, software engineering, and cloud technologies, enabling enterprises to build digital experiences and strengthen customer relationships globally | Software Development | 🇹🇷 Istanbul | 542 | 2000 |
| 11 | [Academy](https://www.tamtam.ai/c/academy) (inkaik.com)<br>Specializing in HR research, selection, project-based staffing, HR consultancy, management consultancy, and payroll services with a focus on professionalism and confidentiality | Human Resources Services | 🇹🇷 Istanbul | 537 |  |
| 12 | [mediSMART Contract Research Organization](https://www.tamtam.ai/c/medismart-contract-research-organization) (medismart.com.tr)<br>Clinical Research Organization in Turkey, offering efficient solutions for drug development with a team of over 350 employees | Research Services | 🇹🇷 Istanbul | 472 | 2008 |
| 13 | [Eksen](https://www.tamtam.ai/c/eksen) (eksen.eu)<br>Independent market research agency offering qualitative and quantitative fieldwork in emerging markets, specialized in various sectors with ISO 20252:2012 certification | Market Research | 🇹🇷 Istanbul | 426 | 2004 |
| 14 | [OKUL YAPI](https://www.tamtam.ai/c/okul-yapi) (okulyapi.com)<br>Innovative and effective educational spaces designed by OKULYAPI for future generations, providing turnkey projects and various classroom concepts in Turkey | Architecture and Planning | 🇹🇷 Istanbul | 422 | 2008 |
| 15 | [BDO Türkiye](https://www.tamtam.ai/c/bdo-turkiye) (bdo.com.tr)<br>An audit and consultancy organization providing professional services in Audit & Assurance, Tax, Social Security, Accounting, and Advisory across the globe | Accounting | 🇹🇷 Istanbul | 414 | 1981 |
| 16 | [DefineX](https://www.tamtam.ai/c/definex) (teamdefinex.com)<br>A forward-thinking consulting house and venture builder focused on digital acceleration, innovation, and cultivating talent for the success of tomorrow | Business Consulting and Services | 🇹🇷 Istanbul | 405 | 2019 |
| 17 | [KoçZer](https://www.tamtam.ai/c/koczer) (koczer.com)<br>Leader in procurement & supply chain management with 20+ years of experience, providing end-to-end solutions, strategic roadmaps, mass purchases, and technological solutions | Business Consulting and Services | 🇹🇷 Istanbul | 390 | 2003 |
| 18 | [Sistem Global Danışmanlık A.Ş.](https://www.tamtam.ai/c/sistem-global-dan-smanl-k-a-s) (sistemglobal.com.tr)<br>Provider of financial, legal, and consultancy services for technology companies, specializing in corporate finance, tax, audit, patents, and international funds | Business Consulting and Services | 🇹🇷 Istanbul | 368 | 1996 |
| 19 | [Subaşı Gümrük Müşavirliği A.Ş.](https://www.tamtam.ai/c/subas-gumruk-musavirligi-a-s) (subasi.net)<br>Established in 1948 as a Customs Brokering entity, employing a skilled team of 470 individuals including 27 customs advisors Specializing in customs clearance services and ensuring accurate, efficient processing through detailed analysis of goods and compliance with relevant regulations | Transportation, Logistics, Supply Chain and Storage | 🇹🇷 Istanbul | 364 | 1948 |
| 20 | [Autoban](https://www.tamtam.ai/c/autoban) (autoban.com)<br>Internationally renowned studio specializing in architecture, interiors, product design, and experiential design with a focus on storytelling, craftsmanship, and sensory experiences | Architecture and Planning | 🇹🇷 Istanbul | 360 | 2003 |
| 21 | [SUR MALİ MÜŞAVİRLİK](https://www.tamtam.ai/c/sur-mali-musavirlik)<br>Providing accounting and financial consultancy services for individuals and businesses, including bookkeeping, financial statements, tax filings, and advisory services | Accounting | 🇹🇷 Istanbul | 355 | 2009 |
| 22 | [MEDEX SMO](https://www.tamtam.ai/c/medex-smo) (medex-smo.com)<br>Specializing in managing clinical research sites, providing site management services to improve trial enrollment, compliance, and performance for pharmaceutical and biotechnology companies | Medical Practices | 🇹🇷 Istanbul | 349 | 2013 |
| 23 | [E Mali Müşavirlik](https://www.tamtam.ai/c/e-mali-musavirlik) (emusavirlik.com)<br>Specializing in advisory services in Mali, providing expert guidance and consulting solutions to clients | Financial Services | 🇹🇷 Istanbul | 345 | 2015 |
| 24 | [Forvis Mazars Türkiye](https://www.tamtam.ai/c/forvis-mazars-turkiye) (forvismazars.com)<br>Global professional services firm serving over 1,500 companies worldwide with a team of 350+ professionals across multiple offices, committed to highest standards and ethics | Accounting | 🇹🇷 Istanbul | 334 | 1977 |
| 25 | [FEV Türkiye](https://www.tamtam.ai/c/fev-turkiye) (fev.com)<br>A provider of turnkey engineering solutions in the automotive industry, specializing in vehicle development, software, autonomous driving, and propulsion systems | Motor Vehicle Manufacturing | 🇹🇷 Istanbul | 330 | 2011 |
| 26 | [Solvia Digital Solutions](https://www.tamtam.ai/c/solvia-digital-solutions) (solviads.com)<br>Design, integrate, and optimize SAP and IT solutions to enhance agility, resilience, and long-term digital transformation for businesses. | IT Services and IT Consulting | 🇹🇷 Istanbul | 318 | 2014 |
| 27 | [RİSUS INTERNATIONAL](https://www.tamtam.ai/c/risus-international) (risusinternational.com)<br>Specializing in change management, analysis, and training services to improve organizational performance through customized solutions and development programs | Human Resources Services | 🇹🇷 Istanbul | 244 | 2006 |
| 28 | [VİZYON](https://www.tamtam.ai/c/vizyon) (vizyongrubu.com)<br>Specializing in tax, auditing, and consulting services to provide comprehensive financial guidance and support to clients | Financial Services | 🇹🇷 Istanbul | 233 | 1984 |
| 29 | [ZETAŞ ZEMİN TEKNOLOJİSİ A.Ş.](https://www.tamtam.ai/c/zetas-zemin-teknolojisi-a-s)<br>A leading geotechnical company providing soil mechanics, foundation engineering, design, contracting, and consultancy services for domestic and international projects | Construction | 🇹🇷 Istanbul | 233 | 1988 |
| 30 | [Wellpoint](https://www.tamtam.ai/c/wellpoint-istanbul) (wellpoint.com.tr)<br>Wellpoint is a health group focusing on occupational health and safety, offering innovative services, training programs, healthcare support, and brand management solutions | Hospitals and Health Care | 🇹🇷 Istanbul | 213 | 2007 |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 12, 2026.

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- [IT Services and IT Consulting companies in Istanbul](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-istanbul) (69)
- [Consumer goods companies in Istanbul](https://www.tamtam.ai/l/consumer-goods-companies-istanbul) (68)
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- [Logistics companies in Istanbul](https://www.tamtam.ai/l/logistics-companies-istanbul) (53)
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- [Financial Services companies in Istanbul](https://www.tamtam.ai/l/financial-services-companies-istanbul) (47)

## The same list elsewhere in Turkey

- [Professional services firms in Turkey](https://www.tamtam.ai/l/professional-services-firms-turkey) (74)

## The same list elsewhere

- [Professional services firms in the world](https://www.tamtam.ai/l/professional-services-firms-in-the-world) (24,737)
- [Professional services firms in the Middle East](https://www.tamtam.ai/l/professional-services-firms-in-the-middle-east) (253)

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Source: https://www.tamtam.ai/l/professional-services-firms-istanbul