The midfielder, who spent the first half of last season on loan at Highbury, has linked up with the League 2 club for the remainder of the current campaign.
Marrow re-signed for Rovers early in the summer as the former Academy graduate joined from Crystal Palace, but after starting the first three matches this season he has found opportunities increasingly limited.
Boss Gary Bowyer feels the move will be a good one for the 23-year-old as it will enable Marrow to get more matches under his belt.
"He needs to play games," said Bowyer. "He came back and did ever so well for us at the start.
"Then we felt we just needed to just change it a little bit in midfield and we were able to bring Corry Evans and Tom Cairney in, whilst Lee Williamson came back from injury.
"So it has been tough for Alex but he now has this opportunity to go and play games and that should suit everybody concerned."
Fleetwood are back in action this Saturday when they take on Hartlepool United at the Highbury Stadium.