Victor Camarasa's classy second-half strike had looked set to secure a precious victory for Cardiff, before headers by Cesar Azpilicueta and Loftus-Cheek saved Maurizio Sarri's side.
In a goalless first-half, Pedro curled a shot over and Willian went close with a free-kick for Chelsea, while Josh Murphy flashed an angled shot narrowly wide at the other end.
A minute after half-time, Harry Arter crossed low and Camarasa calmly clipped in a first-time finish.
Eden Hazard's introduction from the bench bolstered Chelsea's attack and Azpilicueta's late header from Marcos Alonso's 84th-minute flick-on brought them level.
In the first minute of added time Loftus-Cheek appeared at the far post to plant a firm header of his own from Willian's centre past Neil Etheridge.
Chelsea stay sixth, but move level with Arsenal on 60 points.
Neil Warnock's men remain 18th on 28 points, five behind 17th-placed Burnley.