Teenage striker Dominic Poleon fired Leeds into the next round as they won 2-1 against a Chesterfield side who left with their heads held high.
Leeds have never lost a first-round tie in the League Cup, while the Spireites have now fallen at the first hurdle in the last seven seasons. Yet it was the Sky Bet League Two side who seized a shock 19th-minute lead.
Tendayi Darikwa created space on the right for skipper Drew Talbot, whose measured cross to the far post was headed firmly home by striker Eoin Doyle past Leeds keeper Paddy Kenny who was making his 600th career appearance.
Leeds restored their pride with two goals in four minutes, though. First Michael Brown's 28th-minute strike from 20 yards brought his first goal since November. Then Ryan Edwards lost out to Poleon who advanced to the 18-yard box before shooting into the bottom-left corner.
Darikwa should have restored parity but delayed his shot just long enough for Jason Pearce to clear off the line.
Everton, Southampton and Tottenham were beaten by Leeds in cup competitions at Elland Road last season but Chesterfield were far from over-awed, with Gary Roberts impressing.
An angry Roberts felt he should have had a 50th-minute penalty when brought down by Zac Thompson but referee Carl Boyeson ruled the offence to be outside the box.
Visiting keeper Tommy Lee pulled off a full-length save to prevent Luke Murphy's second goal in as many games for Leeds while Nathan Smith struck an upright for Chesterfield in added time.