This was the Blues’ first outing since they sacked manager Liam Rosenior on Wednesday following a run of seven defeats in eight matches (W1), with interim head coach Calum McFarlane tasked with finding an improvement against a Leeds side unbeaten in their previous seven games (W4, D3).
McFarlane would have been encouraged by his team’s confident start, but the first big chance of the game fell to the Whites in the 15th minute, when Robert Sanchez denied Brenden Aaronson with his boot after the forward was put through one-on-one.
Chelsea's top goalscorer Joao Pedro (G19) returned to the starting line-up after missing the past two games due to injury, and the striker came even closer to an opener when he fired against the inside of the post from a tight angle.
The Blues had failed to score in their previous three matches, but they ended their drought in the 23rd minute when Pedro Neto crossed for the unmarked Fernandez to head home his 13th goal of the season across all competitions - and the skipper’s first since he was dropped by Rosenior last month over comments about his future at Stamford Bridge.
This was Leeds’ first FA Cup semi-final since 1987 and their players were perhaps overawed by the occasion, with Chelsea fully deserving their half-time lead.
Leeds boss Daniel Farke made a double substitution and switched to a back four at the break in an effort to turn the tide, with Anton Stach and Joe Rodon replacing James Justin and Jaka Bijol.
Stach almost equalised with his very first touch when he unleashed a thunderous effort from outside the box, requiring Sanchez to parry over the crossbar, before Pedro failed to make clean contact from six yards out and the ball bobbled wide.
Leeds were looking much more threatening, and Dominic Calvert-Lewin headed straight at Sanchez shortly after.
Despite their second-half improvement, the Whites failed to find an equaliser and they have now lost 1-0 on all three of their visits to the new Wembley.
Their wait for a first FA Cup final since 1973 goes on, and attention now returns to confirming Premier League safety in the final four games of the season.
In contrast, eight-time FA Cup winners Chelsea have the chance to salvage some silverware from a disappointing campaign in the final on May 16, and remain unbeaten against Leeds in this competition (W7, D3).
Flashscore Man of the Match: Enzo Fernandez (Chelsea)