The England Under-21 international made the temporary switch to south Wales in September, with the deal originally set to expire on December 26.
Morrison made seven Championship appearances for Cardiff, six of which were from the bench.
On Monday, the Welsh outfit released a brief statement declaring that Morrison would return to Upton Park for unspecified personal reasons.
"Due to personal circumstances, Cardiff City have allowed Ravel Morrison compassionate leave and permission to train in more familiar surroundings at this time with his parent club, West Ham United," the statement read.
Morrison was impressive for West Ham in the first half of the Premier League season in 2013-14, but was then loaned out to QPR, whom he helped to promotion from the second tier.
It remains to be seen whether he will feature in Sam Allardyce's plans, with fourth-placed West Ham enjoying a superb campaign.
