Acquisitions and mergers
| 2023 | Acquisition of MentorMate, annual revenue USD 65 million |
| 2019 | Merger of Tieto and EVRY completed in December |
| 2019 | Meridium AB, annual revenue around EUR 6 million |
| 2018 | NSEC AB, annual revenue EUR 4 million |
| 2018 | Petrostreamz, annual revenue EUR 2 million |
| 2017 | Avega Group AB, annual revenue EUR 45 million |
| 2016 | Emric, annual revenue EUR 20 million |
| 2015 | Software Innovation, annual revenue EUR 41 million |
| 2015 | Imano AB, annual revenue EUR 7 million |
| 2015 | Smilehouse, annual revenue around EUR 10 million |
| 2014 | Part of Siemens Convergence Creators Network Directory Server (NDS), IP Multimedia Systems (IMS), Home Location Register (HLR) and Radio Access (RA) businesses |
| 2014 | FD Finanssidata |
| 2013 | Canvisa Consulting |
| 2010 | T&T Telecom |
| 2010 | Tieto Broadcasting IT Oy |
| 2010 | TrustInfo |
| 2009 | TKP Tieto |
| 2008 | FD Finanssidata |
| 2008 | Primasoft |
| 2007 | Abaris AB, Sweden |
| 2007 | Provisio AB, Sweden |
| 2007 | Fortuna Technologies Pvt. Ltd., India |
| 2006 | Waldbrenner AG, Germany |
| 2006 | Manpower's HR services, Sweden |
| 2006 | RTS Networks Ltd., Poland |
| 2006 | Laps Care AB, Sweden |
| 2006 | Cymed AG, Germany |
| 2005 | S.E.S.A. Software und Systeme AG, Germany |
| 2005 | Pentec Ltd, Great Britain |
| 2005 | Attentiv Systems Group, Great Britain |
| 2005 | SIA IT Alise, Latvia |
| 2005 | Zait IT Tjänster AB, Sweden |
| 2005 | Comnet S.P.A., Italy |
| 2005 | Waldbrenner AG, Germany |
| 2004 | Ki Consulting & Solutions AB, Sweden |
| 2004 | Respons AS, Norway |
| 2004 | Doctorex, Finland |
| 2004 | C&S Healthcare Software AB and C&S Management AB, Sweden |
| 2004 | Informations, Logik Sweden AB and Informations, Logik Netherlands B.V |
| 2004 | ITB AG, Germany |
| 2004 | S.E.S.A. AG, Germany |
| 2003 | Inveos AG, Germany |
| 2002 | Sykora, Germany, Czech Republic |
| 2002 | Majiq, USA |
| 2002 | Ementor Financial Systems, Norway |
| 2001 | Softema, Finland |
| 2000 | European Medical Solutions Group, Norway |
| 2000 | Sypro System Professionals Oy |
| 1999 | Enator AB, Sweden |
| 1999 | Entra Data AB, Sweden |
| 1998 | Konts SIA, Latvia |
| 1998 | Oy Tietokonepalvelu Ab |
| 1997 | Huld & Lillevik AS, Norway |
| 1996 | AXO Systems AS, Norway |
| 1996 | Avancer Oy |
| 1995 | Unic Oy |
| 1995 | VTKK-yhtymä Oy |
| 1995 | Procons Data Oy |
| 1995 | Dativo Oy |
| 1994 | Suunnittelu ja laskenta Oy |
| 1994 | Financial Software Technology Oy |
| 1993 | Datacity Information Systems Oy |
| 1993 | Carelcomp Oy |
| 1990 | Finnish Data Power Oy |
| 1990 | Tietoässä Oy |
| 1987 | Datema AB, Sweden |
| 1987 | Nokia computer center |
| 1984 | Tietojyvä Oy |
| 1983 | Avonius Oy |
| 1976 | Finnsystems Oy |