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.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 | 4,336 | ||||
| 2 |
Serbest Muhasebeci Mali Müşavirlik Hizmetlerismmmemrahkucukdeniz.com
An accounting office in Istanbul providing practical solutions to tax issues for clients nationwide, focusing on communication, trust, and quality service |
3,332 | |||
| 3 |
KUCUKYiLMAZ Consulting Co.facebook.com
With 25 years of experience in the friction industry, offering assistance in compounding, process, product, and business development, representing major suppliers |
2,363 | |||
| 4 |
KPMG Türkiyekpmg.com
Providing audit, tax, and advisory services to diverse industries with a sector-focused approach and extensive local and international expertise. |
1,446 | |||
| 5 |
BGTSbilgeadam.com
An international technology consulting firm specializing in software development, IT consulting, business processes, QA & testing, big data, cloud, AI/ML, and cybersecurity services |
1,182 | |||
| 6 | 870 | ||||
| 7 |
Özel bir danışmanlık şirketikml.com.tr
Strategic planning, brand management, marketing, sales management, R&D, innovation, HR, supply chain, quality management, IT, corporate governance, digital transformation, corporate training |
705 | |||
| 8 | 702 | ||||
| 9 |
adesso Turkeyadesso.com.tr
A digital transformation company with agile beliefs, employing over 10,000 people worldwide, offering custom software development and IT solutions |
628 | |||
| 10 |
Commenciscommencis.com
A company specializing in experience design, software engineering, and cloud technologies, enabling enterprises to build digital experiences and strengthen customer relationships globally |
542 | |||
| 11 | 
Academyinkaik.com
Specializing in HR research, selection, project-based staffing, HR consultancy, management consultancy, and payroll services with a focus on professionalism and confidentiality |
537 | |||
| 12 |
mediSMART Contract Research Organizationmedismart.com.tr
Clinical Research Organization in Turkey, offering efficient solutions for drug development with a team of over 350 employees |
472 | |||
| 13 | 426 | ||||
| 14 |
OKUL YAPIokulyapi.com
Innovative and effective educational spaces designed by OKULYAPI for future generations, providing turnkey projects and various classroom concepts in Turkey |
422 | |||
| 15 |
BDO Türkiyebdo.com.tr
An audit and consultancy organization providing professional services in Audit & Assurance, Tax, Social Security, Accounting, and Advisory across the globe |
414 | |||
Want more companies than this list?This page shows the largest ones only. Connect to Tamtam to see every company that matches, filter by size, industry or growth, and reach their decision-makers. | |||||
| 16 |
DefineXteamdefinex.com
A forward-thinking consulting house and venture builder focused on digital acceleration, innovation, and cultivating talent for the success of tomorrow |
405 | |||
| 17 |
KoçZerkoczer.com
Leader in procurement & supply chain management with 20+ years of experience, providing end-to-end solutions, strategic roadmaps, mass purchases, and technological solutions |
390 | |||
| 18 |
Sistem Global Danışmanlık A.Ş.sistemglobal.com.tr
Provider of financial, legal, and consultancy services for technology companies, specializing in corporate finance, tax, audit, patents, and international funds |
368 | |||
| 19 |
Subaşı Gümrük Müşavirliği A.Ş.subasi.net
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 |
364 | |||
| 20 |
Autobanautoban.com
Internationally renowned studio specializing in architecture, interiors, product design, and experiential design with a focus on storytelling, craftsmanship, and sensory experiences |
360 | |||
| 21 |
SUR MALİ MÜŞAVİRLİK
Providing accounting and financial consultancy services for individuals and businesses, including bookkeeping, financial statements, tax filings, and advisory services |
355 | |||
| 22 |
MEDEX SMOmedex-smo.com
Specializing in managing clinical research sites, providing site management services to improve trial enrollment, compliance, and performance for pharmaceutical and biotechnology companies |
349 | |||
| 23 |
E Mali Müşavirlikemusavirlik.com
Specializing in advisory services in Mali, providing expert guidance and consulting solutions to clients |
345 | |||
| 24 |
Forvis Mazars Türkiyeforvismazars.com
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 |
334 | |||
| 25 |
FEV Türkiyefev.com
A provider of turnkey engineering solutions in the automotive industry, specializing in vehicle development, software, autonomous driving, and propulsion systems |
330 | |||
| 26 |
Solvia Digital Solutionssolviads.com
Design, integrate, and optimize SAP and IT solutions to enhance agility, resilience, and long-term digital transformation for businesses. |
318 | |||
| 27 |
RİSUS INTERNATIONALrisusinternational.com
Specializing in change management, analysis, and training services to improve organizational performance through customized solutions and development programs |
244 | |||
| 28 |
VİZYONvizyongrubu.com
Specializing in tax, auditing, and consulting services to provide comprehensive financial guidance and support to clients |
233 | |||
| 29 |
ZETAŞ ZEMİN TEKNOLOJİSİ A.Ş.
A leading geotechnical company providing soil mechanics, foundation engineering, design, contracting, and consultancy services for domestic and international projects |
233 | |||
| 30 |
Wellpointwellpoint.com.tr
Wellpoint is a health group focusing on occupational health and safety, offering innovative services, training programs, healthcare support, and brand management solutions |
213 | |||
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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.
More company lists in Istanbul
- The largest companies in Istanbul 1,393
- Multinational companies in Istanbul 348
- Manufacturers in Istanbul 249
- Retail chains in Istanbul 188
- Companies with in-house R&D in Istanbul 177
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- Corporate groups and holding companies in Istanbul 134
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- Education providers in Istanbul 93
- Financial services firms in Istanbul 81
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- Retail companies in Istanbul 71
- IT Services and IT Consulting companies in Istanbul 69
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- Hardware manufacturers in Istanbul 66
- Energy companies in Istanbul 64
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- Construction companies in Istanbul 59
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- Logistics companies in Istanbul 53
- IT services companies in Istanbul 50
- Financial Services companies in Istanbul 47