The Mirror's Darren Lewis has reported fitness concerns could still hold up the deal, however.
Nasri is finishing up an 18-month doping ban and will be able to join up with a new club and play by the end of December. He's been allowed to train since November, per the report, and West Ham has moved quickly.
Sportswriter John Brewin couldn't help himself:
Nasri worked under Hammers manager Manuel Pellegrini at City, where he was a vital part of his teams. The 31-year-old is seen as a short-term replacement for Andriy Yarmolenko, who is out for the season.
The Frenchman will sign a six-month contract with an option for an additional year. The £80,000 wages are high, prompting football writer Jake Humphrey to wonder how it might impact contract talks with 19-year-old talent Declan Rice:
Per Football.London's Sam Inkersole, Rice told the Times he's eager to stay with the east London club, amid speculation linking him with several other teams.
Nasri last played for Turkish side Antalyaspor, but his contract was terminated after the doping ban became official. He played in the Premier League between 2008 and 2016 before leaving City for a one-year loan with Sevilla.
Per Lewis he's badly out of shape, raising questions about te deal. Yarmolenko, Jack Wilshere and Andy Carroll have given the team enough fitness concerns already.
West Ham spent big in the summer on the likes of Felipe Anderson, Issa Diop and Yarmolenko but have fallen short of the expectations so far. They are 13th place in the Premier League standings, having won just one of their last five matches.
With 14 goals scored, the attack ranks in the middle of the Premier League pack, and the hope is the introduction of the creative Nasri could change that. His fitness is a concern, but with his ban yet to end, West Ham have ample time to do their homework.