Hochtief will build new or expanded ticket halls at West Drayton, Hayes & Harlington and Southall stations; Graham will carry out similar construction works at Acton Main Line, West Ealing and Ealing Broadway under a £46.6m contract.
The work is needed to cope with an anticipated increase in passenger numbers after the Elizabeth Line (Crossrail) eventually begins operations.
The stations will also get improved accessibility with lifts and footbridges that will bring step free access to all platforms serving the Elizabeth line.
In 2018/19 Network Rail delivered the enabling works for the new station buildings by installing the foundations and steel frames for new accessible footbridges and lift shafts. The new ticket halls and step free access will be completed by December 2020.
Network Rail project director Dave Corkett said: “With the enabling works already complete, the award of contracts for Southall, Hayes & Harlington, West Drayton, Ealing Broadway, West Ealing and Acton Main Line stations will allow Network Rail and its new contractors to deliver these important station upgrades that are so eagerly awaited by local communities in west London.”