With more than 34,000 FTE employees and around 5,200 branches in over 60 countries and territories around the world, The Adecco Group offers a wide variety of services that include temporary staffing, permanent placement, career transition, re-skilling and talent development, as well as outsourcing and consulting. The Adecco Group key markets are France, North America, United Kingdom and Ireland, Japan, Germany, Austria, Italy, Benelux, Nordics, Iberia, Australia, New Zealand, and Switzerland.
The Adecco Group is the parent company of various brands including Adecco Staffing, Euro Engineering, Modis, Spring Professional, Badenoch & Clark, Pontoon, General Assembly, Vettery, YOSS , Adia and Lee Hecht Harrison.
As for staffing, The Adecco Group covers many sectors, including office, industrial, technical, financial and legal, amongst others.
- 1996: Personnel services firms Ecco and Adia Interim merge to form a global company with annualised revenues of €5.4 billion. Operations are combined to form a network of 2,500 branches. The core staffing business consists of 250,000 staff situated with various companies.
- 2000: The Adecco Group acquires Olsten Staffing, becoming the largest recruitment company in the U.S. The merged company generates combined revenues of €11.6 billion.
- 2002: The Adecco Group consolidates its businesses and creates divisions to manage its business.
- 2005: The Adecco Group expands across six professional business lines defined by occupational fields and now provides all services under one name.
- 2006: Following the acquisition of DIS AG, Germany, Dieter Scheiff assumes the position of Chief Executive Officer of The Adecco Group. Dominik de Daniel becomes Chief Financial Officer.
- 2007: The annual shareholders' meeting approves the nomination of Jürgen Dormann, former Vice Chairman, as Chairman of the Board. Rolf Dörig becomes Vice-Chairman. Klaus J. Jacobs, the co-founder of Adecco, hands back his mandate, having reached the statutory retirement age.
- 2008: On 11 September, Klaus J. Jacobs, founder and Honorary President of The Adecco Group, dies. Jürgen Dormann steps down at year end, as Chairman of the Board of Directors.
- 2009: Rolf Dörig starts as Chairman of the Board of Directors of the Adecco Group. On 1 June, Patrick De Maeseneire takes over as Chief Executive Officer of the Adecco Group from Dieter Scheiff. The Adecco Group acquires Spring Group in the UK, and tables an offer for MPS Group.
- 2010: The acquisition of MPS Group officially closes. The Adecco Group sets up a joint venture in Shanghai with Chinese HR services company Fesco.
- 2011: FESCO Adecco begin operations on 1 January. The Adecco Group announces the acquisition of US-based Drake Beam Morin, Inc.
- 2012: The Adecco Group acquires VSN Inc., a provider of professional staffing services in Japan. Henri-Ferdinand Lavanchy, the founder of Adia, passes away.
- 2014: The Adecco Group acquires OnForce to expand its Beeline service offering, creating a unique integrated solution for managing contingent workforces. The Jacobs Group sells the vast majority of its 18% stake in the Adecco Group.
- 2015: On 11 March, The Adecco Group acquires Knightsbridge Human Capital Solutions, a market leader in Canada in career transition, talent and leadership development and recruitment services. On 1 September, Alain Dehaze takes over as Chief Executive Officer of The Adecco Group from Patrick De Maeseneire. The Adecco Group announces a new composition of the Executive Committee.
- 2016: On 10 May, The Adecco Group closes the acquisition of Penna Consulting Plc, a UK company providing career transition and talent development services as well as recruitment services. The acquisition complements the activities of Lee Hecht Harrison.
- 2018: The Adecco Group acquires General Assembly  and Vettery
The Adecco Group operates in the market through many different brands. The main international ones are:
- Spring Professional
- Badenoch & Clark
- Lee Hecht Harrison
- General Assembly
Following on from their sponsorship between 2002 and 2007; in September 2015, The Adecco Group signed a three-year extension as an international sponsor and Official HR partner of the ITF’s two team competitions, Davis Cup by BNP Paribas and Fed Cup by BNP Paribas.
The agreement started with the 2015 Davis Cup World Group semifinals and play-offs and continues through to 2019.
Adecco also sponsored the Norwegian First Division (as Adeccoligaen) from 2005 until 2013.
Modis, one of the Adecco Group's brands dedicated to professional services for IT, engineering and life sciences, becomes the Official Innovation Partner of electric racing championship Formula E, announcing it during the Formula E Rome E-prix in 2018. 
On 10 December 2008, Adecco UK Ltd applied to the Company Names Tribunal under s.69(1)(b) Companies Act 2006 for a change of name of Adecco UK Recruitment Ltd, which had been registered at Companies House since 14 October 2008.
The application went undefended by the respondent and the adjudicator ordered on 3 March 2009 that Adecco UK Recruitment Ltd must change their name within one month. Additionally the respondent was ordered not to cause or permit any steps to be taken to register another company with an offending name which could interfere, due to its similarity, with the goodwill of the applicant.
Adecco UK Recruitment Ltd was also ordered to pay a contribution towards Adecco UK Ltd's costs.