The company, which has 150 stores in the UK, recently embarked on an ambitious change programme, which is centred on an overhaul of its IT systems.
The outsourcing deal, announced last week, is an initial part of the programme, said Maurice Boardman, head of IT at Matalan.
Cap Gemini will manage Matalan's helpdesk, desktop services, networks and application support and development.
About 40 IT staff will transfer to Cap Gemini under Tupe regulations.
IT strategy, project and business systems management will remain in-house, ensuring that Matalan remains in charge of the key skills required for the change programme, Boardman said.