The 26-year-old, who was one of South Africa`s stand-out performers at the 2010 Word Cup, will be available for the clash with Sheffield United on Saturday.
Dikgacoi told the club`s official website: "I'm very pleased with the move. It's a chance to get some game time and that will help my chances of playing for my national team.
"I know (the Championship) is quite an intensive league so it should be an interesting week and I'm looking forward to the game on Saturday."
Palace manager Dougie Freedman said: "He's an experienced international who has played in England for a while now, so he will have adapted to that.
"He's an athletic player who can sit in the midfield and add experience for us."