Didier Drogba's 84th-minute winner put Chelsea in the FA Cup final and kept alive interim manager Guus Hiddink's hopes of an unlikely treble.
Drogba struck at the end of a poor semi-final when he beat Arsenal goalkeeper Lukasz Fabianski to Frank Lampard's long ball and rolled the ball home.
The Gunners had taken an early lead through Theo Walcott's deflected shot but had struggled to live with Chelsea from that moment.
Florent Malouda levelled before half-time with a low shot that beat Fabianski at his near post and, although the Gunners dug in after the break, Chelsea probably deserved their victory and a return to Wembley in the final on 30 May.
As a spectacle, this game did not come close to the drama and intensity of the Blues' last outing - their midweek 4-4 draw with Liverpool at Stamford Bridge that saw them reach the Champions League semi-finals with a 7-5 aggregate win.
But Hiddink, whose side also remain with an outside chance of snatching the Premier League title, will not mind one bit after seeing his side put on a performance of power and patience to progress.