A statement from Palace, who play in the second tier of English football, says the loan deal is till the end of the season.
Dikgacoi could make his Palace debut against Sheffield United on Saturday.
He has made just one substitute appearance under new Fulham boss Mark Hughes and was linked with a January move away from Craven Cottage.
But Fulham triggered a clause in his contract to tie him to the club for a further year.
He was part of the Bafana Bafana squad at the 2010 World Cup which South Africa hosted.
Source: BBC Sport
Source: BBC Sport