Villa are hoping the England Under-21 skipper will put pen to paper on Thursday subject to him passing a medical and agreeing personal terms.
Reo-Coker is poised to sign a four-year deal which will keep him at Villa Park until the summer of 2011.
It will be Villa manager Martin O'Neill's first summer signing with more expected to follow in the next couple of weeks.
Villa made an initial offer of £7million for Reo-Coker but have had to increase their bid for a player who cost just £500,000 when he moved from Wimbledon to Upton Park three and a half years ago.
Reo-Coker was part of the England squad in the European Under-21s Championships last month and will take a holiday before joining up with his new team-mates in two weeks.
O'Neill has been keen to sign the player since he slapped in a transfer request at the end of last season.
Manchester City made a last-ditch attempt to try and sign Reo-Coker but Villa were always in the driving seat.
Villa are in urgent need of new midfield blood after losing Gavin McCann to Bolton while Steven Davis is set to move to Fulham in a £4million deal.
O'Neill will now turn his attention to Tottenham striker Jermain Defoe while he is also keen on Chelsea winger Shaun Wright-Phillips.
Villa owner Randy Lerner jetted in from America on Monday to start bankrolling O'Neill's summer spending spree.
A Villa spokesman said: "Aston Villa have agreed a fee with West Ham for Nigel Reo-Coker subject to a medical and agreeing personal terms which will hopefully be confirmed tomorrow."