The 23 year-old has made 15 appearances for Arsenal in all competitions this campaign, although just two of those have been Premier League starts.
He has not appeared for Mikel Arteta's side in the league since coming on as a substitute in the 3-1 win over Tottenham on 1 October.
Belgium international Lokonga will now spend the next four months with Palace, who are managed by former Arsenal midfielder Patrick Vieira.
Palace confirmed the news on their official website on Wednesday (AEDT), shortly after Arsenal completed the signing of Jorginho from Chelsea to provide adequate midfield cover.
"I'm really excited – I can't wait to get started. I'm really happy to join Crystal Palace," Lokonga told the club's official website.
"I want to go as far as possible with the team. I will try to push for me and the team to do the maximum to reach the top."
Lokonga, who has played 39 times for Arsenal in total since joining from Anderlecht in July 2021, is in line to make his Palace debut away at Manchester United on Saturday.
