Martin, 22, signed a two-and-a-half year deal at The Den this evening after Palace boss Neil Warnock accepted a bit of £50,000 from The Lions for the player's services.
"David will give the team pace and balance as a wide left sided player," Jackett told the club's official site. "I expect hm to go straight into the squad for Saturday's game against Doncaster."
With Ryan Smith and Chris Hackett both out with long-term injuries, Jackett was keen to bring in a wide man, having tried the likes of Neil Harris and Zoom Bakayogo on the flanks, and has been playing Arsenal striker Jay Simpson out wide in the hope of getting a bit of width. For his part, Martin is looking forward to the challenge ahead.
"I've known this move has been on the cards for a few weeks now," said the winger. "But it wasn't clear that it might actually happen until a few hours before the deadline.
"I'm really pleased everything's done now and I'm looking forward to the chance of regular first team football with Millwall."