The Swedish international has spent a month at Upton Park, and the East London outfit were keen to prolong the temporary move.
However, the midfielder has cited 'personal reasons' behind his decision to return north.
Alexandersson will be striving to challenge for a place in David Moyes's starting line-up, with the Merseysiders failing to impress in a drab goalless draw with Southampton at Goodison Park on Sunday afternoon.
He joined The Hammers on September 11, and figured in seven of their games.
