Original Sheffield Council cost estimates valued improvement works at around £14.3m but Apollo swooped in to secure the job with a £9.9m bid ahead of its five rival bidders.
The line-up consisted of Bullock Construction, G F Tomlinson, Henry Boot Construction, Thomas Vale and Wates.
Reports have suggested that the second lowest tender was only £100,000 higher than Apollo’s.
The fiercely-contested Decent Homes project involves upgrading doors, windows, kitchens and bathrooms at around 200 homes, some in three 16-storey tower blocks.
Apollo will also improve external wall insulation on around 40 four and five-storey houses, using an insulated render and high density timber cladding.
Work is due to start in June and be complete in 2013.
Apollo regional director Dan Germann said: “The contract was stated on OJEU as £12m and our bid was priced competitively in line with tender requirements.
“We are extremely pleased at winning Sheffield which will help cement our position in the north and look forward to working with the client to deliver the scheme and strengthen our business in the region.”
Derek Martin, director of housing, enterprise and regeneration for Sheffield Council said: “Apollo have been successful in a rigorous and thorough tendering process which evaluates on price and quality.
“We have every confidence in Apollo’s ability to deliver the right quality of work in return for our investment and we look forward to working with them on this contract.”