The defender, who has spent his career in the lower leagues of British football, has made three appearances for League Two this season.
"Everyone at Morecambe FC is deeply saddened to learn of the death of Christian Mbulu and wishes to express their sincere condolences to his family and friends during this very sad time," the club announced on Tuesday on its official Twitter channel.
One of his former teams, the Scottish club Motherwell, also paid tribute to the young player who played six matches with the first team last season.
"We are shocked to hear the news of Christian's death," said Motherwell president Jim McMahon.
"He was a young man so friendly, pleasant and dedicated that we liked to have around Fir Park.
"Our thoughts are with his family during this incredibly difficult time. We hope that their privacy will be respected by everyone as they try to cope with their loss."
Mbulu began his professional career in Millwall before representing teams such as Crewe and Braintree.
The cause of his death remains to be confirmed.
