Jose Mourinho's side led through a Loic Remy strike at the interval, but a defensive error involving the goalkeeper an John Terry sparked a fightback from the Red Bulls.
Asmir Begovic endured a difficult debut as Chelsea suffered a 4-2 loss to New York Red Bulls in the International Champions Cup.
Loic Remy opened the scoring with an emphatic strike in the first half and had the chance to double the lead, but failed to divert a cross into an open goal.
The Red Bulls were level shortly after the break when second half substitute Begovic was tackled by Franklin Castellanos, who finished into an empty net after a poor pass from John Terry.
Begovic was beaten again midway through the second half by a header from 16-year-old Tyler Adams, before Sean Davis slotted home from close range.
Eden Hazard pulled a goal back for Chelsea but Davis scored again as a disorganised Chelsea back line fell apart after the interval.
The Red Bulls were impressive from the outset on home soil, with Davis sending an early warning shot at Thibaut Courtois, who scrambled across his line following a miscued effort from long range.
Chelsea's physical presence at set-pieces proved troublesome and Branislav Ivanovic and Kurt Zouma almost combined for the opener approaching the midway point of the first half, but the latter was unable to steer his header inside the post.
However, Chelsea were not to be denied seven minutes later thanks to Remy, who adjusted his body, took an extra touch and fired the ball into the net,
having been picked out by Oscar.
It should have been 2-0 four minutes later as Victor Moses scooped the ball over Red Bulls goalkeeper Kyle Reynish, but the winger's shot came back off the upright.
Remy then inexplicably missed from close range in the 40th minute, after somehow kneeing his shot over the crossbar from inside the six-yard box.
At the other end, Courtois was almost embarrassed, having been caught in possession, though he recovered to deny Marius Obekop.
It took five minutes of the second half for the youthful New York outfit to draw level.
After seeing his shot cleared off the line just second earlier, substitute Castellanos pounced on a poor back pass from Terry to round new Chelsea goalkeeper Begovic.
Chelsea continued to be wasteful in the attacking third, as Diego Costa hit the woodwork and skied his follow-up effort over the crossbar just after the hour mark.
That proved costly as the Red Bulls struck with two quick-fire goals.
New York's 16-year-old midfielder Adams found himself unmarked in the box as he glanced a header past Begovic with 20 minutes remaining, and Davis got in on the act three minutes later.
Hazard pulled a goal back for Chelsea almost instantly, but Davis restored his team's two-goal advantage shortly after.
The remaining minutes of the match saw Chelsea occupy their attacking third, though Oscar and Costa wasted golden opportunities.
