Business Employment Services Training Ltd (BEST) provides training and development to job-seekers and employers in south and west Yorkshire.
Interserve is paying an initial £17.5m plus up to £750k later, subject to agreement of completion accounts.
Interserve said that the acquisition increased its delivery of front-line services, particularly in the Department of Work and Pensions' Work Programme. Interserve is already involved in the Work Programme through its Rehab Jobfit joint venture, which has contracts in Wales and the south-west.
BEST's pro forma annual revenue is £17m, generating operating profit of £3m, and its gross assets are valued at £2m. The existing management will stay with the business under the new ownership.
Interserve chief executive Adrian Ringrose said: "The acquisition of BEST reflects our strategy of developing as a top-tier public services provider, delivering front-line services. It builds on our existing relationships with both the DWP and the community in Leeds and the surrounding area, provides a foundation for offering more broadly-based community services and enhances our role in training and skills development."