The Ivorian forward struck on the stroke of half-time to secure a vital result for the Londoners and send them into the second leg at Camp Nou with a slender advantage
Didier Drogba was the hero for the Blues, with his goal on the stroke of half-time giving Roberto Di Matteo's men a lead to protect for the return fixture at Camp Nou.
For the Catalan club, it was a case of what could have been, as a series of missed chances and some resolute defending by the hosts shut them out in England and leaves the tie on a knife edge.
Barca coach Pep Guardiola handed Cesc Fabregas a start in the visiting XI, to mark his first game on English soil since his summer move from Arsenal. Meanwhile, for Chelsea, Drogba was preferred to Fernando Torres in attack after his inspired performance in the 5-1 FA Cup semi-final win against Tottenham on the weekend.
The Ivorian nearly repaid his manager’s faith early on, twice coming close to breaking through on goal on the counter in the opening exchanges.
However, it was the visitors who almost drew first blood after nine minutes. Andres Iniesta lifted a superb pass over the defence into the path of Alexis Sanchez, who lobbed the onrushing Petr Cech, but saw his effort smack off the crossbar.
Barca were monopolising possession, but still appeared vulnerable defensively whenever the ball was in the air, with a Chelsea corner coming within inches of being turned in by the combined efforts of John Terry and Gary Cahill.
With a quarter of an hour gone, Guardiola’s men went close again after Iniesta’s low drive was parried by Cech right into the path of Fabregas, who somehow failed to find the target from eight yards out.
The Catalan midfielder then cut inside Cahill on the left in the 26th minute, before firing a shot that was denied by a strong hand from Cech at the near post.
The Czech keeper was called into action again moments later, this time to smother a header by Lionel Messi, who had gotten on the end of a Dani Alves cross.
Chelsea were doing a good job of containing Barca deep in their own half, but were almost caught out two minutes before half-time. A threaded pass by Messi played in Fabregas, who dinked the ball over Cech, but Ashley Cole rushed back in time to hack the ball off the line.
Then, in the last minute of first-half injury time, Chelsea broke the deadlock. Frank Lampard was able to strip Messi of possession in his own half, before releasing Ramires with a great long pass. The Brazilian advanced into the box, and did just enough to square to Drogba at the far post, who turned the ball home to send the hosts into the break with the lead.
Barca started strongly after the restart, with Adriano carving his way to the top of the box, only to see Cech push his effort away to the right.
A beautiful pass over the top from Fabregas then caught out the Chelsea defence and put Sanchez clean through, but the Chilean could not fully bring the ball under his control and shot wide of the far post from only a few yards out.
Guardiola’s men were finding it difficult to get a clear opening as the second half wore on, with Chelsea getting plenty of men behind the ball to crowd them out.
However, four minutes before the end, Barca nearly found a way back after a glancing header by Carles Puyol from a free kick was parried by Cech at full stretch.
There was even more drama in the last minute of injury time, with Pedro striking the base of the post after a scramble in the box as Chelsea did just enough to hang on.
Both sides have plenty to occupy their attention before the return leg at Camp Nou next Tuesday, with Chelsea visiting Arsenal in the English Premier League, while Barcelona play host to Real Madrid at home in La Liga.