The Cod Army drafted in the 23-year-old left-back at the end of February when Stephen Crainey picked up a two-match suspension.
Even since Crainey’s return, Chicksen has been Graham Alexander’s preferred option in his defence, making seven appearances in total.
“We spoke to Adam a couple of weeks ago about extending his loan until the end of the season,” Alexander told Fleetwood’s official website.
“He was very keen to stay and he is a very good player that has done well for us.
“He came off on Sunday purely for tactical reasons, not due to his performance. We wanted to bring another forward on.
“We are delighted with how he has come in and settled into the group. But, first and foremost, Adam is a very good player.
“We are pleased Brighton have allowed us to keep him until the end of the season so we thank them for that. We are looking forward to the remaining games with Adam in the squad. “