The versatile Jamaican was sent to his fourth MLS team after one year with RSL in exchange for allocation money.
The defender-midfielder was traded to Chicago on Friday for allocation money. Palmer, 29, provides the Fire depth at both fullback spots and in holding midfield.
Acquired in last year's re-entry draft after stints with the Houston Dynamo and Portland Timbers, the Jamaica international appeared in 17 regular season games and three playoff matches for RSL this past season. A 72nd-minute substitute in Sunday's MLS Cup final, Palmer saw his penalty kick ring the crossbar in the shootout's 10th round, giving the title to Sporting Kansas City.
"Real Salt Lake will always have a special place in my heart," Palmer said in a news release. "I wouldn't trade this last season with RSL for anything. If someone said to me at the beginning of the year that we would do it all over again, that RSL and Sporting Kansas City would be in MLS Cup and Kansas City would win, I wouldn't trade teams.
"I wouldn't trade the Real Salt Lake experience for the MLS Cup. That's how much being with RSL, being in Salt Lake City and in Utah meant to me."