Speaking to Exeter City's website, Croll said it was an easy decision for him to make to move to Devon.
"I am delighted," he said. "Last season when I was on loan I really enjoyed my time here and the environment of the club and the management and the players is what made me want to sign.
"It was something that was spoken about at the back end of last season as I knew I was leaving Palace. There were options on the table, but it was just about playing where I felt I was going to progress the most.
"We gave promotion a good go last season and I think we were quite unlucky, but I feel we have got the players and the staff to push forward again.
"It wasn't that tough of a decision (to join Exeter) as even at the back end of last season when I wasn't playing that much, I still wanted to stay at Exeter.
"I am really excited and I can't wait to get back on the pitch."