The Spanish left back beat Michel Vorm late on and Gervinho added a second at the Liberty Stadium to leave the Gunners trailing fourth-place Chelsea by only two pointsNacho Monreal scored his first goal for Arsenal to help the Gunners to a 2-0 victory over Swansea and a crucial three points at the Liberty Stadium.
The new signing from Malaga pounced on a loose ball in the penalty area after 74 minutes before beating Michel Vorm with a low shot that brings Arsene Wenger's team within two points of Chelsea, which plays tomorrow.
Alex Oxlade-Chamberlain twice hit the crossbar but both goalkeepers had remained largely untested until Monreal struck and Gervinho slotted in to complete a counterattack in added time.
Oxlade-Chamberlain stepped past Angel Rangel and hit the crossbar with a sidefooted shot from 12 yards but the home side soon took control, stifling Arsenal's attacks with the numbers it brought back behind the ball.
A neat move in midfield ended in Ki Sung-Yueng threading a through ball into the path of Rangel, but under pressure from two Arsenal defenders, the right back miscued his shot.
Michu did much the same when Carl Jenkinson's poor pass across the edge of his own penalty area was intercepted by Jonathan de Guzman. The Spaniard checked back to wriggle away from Per Mertesacker but scuffed his effort from 15 yards wide of the far post.
Thereafter, though, Swansea struggled to work clear sights of goal just as much as the visitors. Oxlade-Chamberlain again clipped the crossbar, this time from 30 yards, before the half was out but the tempo was desperately slow after the restart.
Arsenal, though, would find the breakthrough from an unlikely source. Olivier Giroud looked to have wasted a good chance when he controlled a Cazorla cross poorly in the Swansea box, but the loose ball ran to Monreal, who drilled a low shot past Vorm.
Swansea's captain, Ashley Williams, had already reminded his teammates that they must not become complacent after their Capital One Cup victory but De Guzman's free kick against the side netting was the closest they came to an equalizer as they slipped to a second straight defeat.
The Swans were always likely to be prone to an Arsenal counterattack as they poured forward in search of a late goal, and Gervinho took advantage by finishing off a break led by Aaron Ramsey.