A 25th-minute corner on the left from Ed Upson was met six yards out by giant centre-half N'Gala and his header crept into the net to settle Saturday's League One clash.
The Glovers had not won away since March, but they were not overly-exerted in ending their run. Defeat for Hartlepool means they have lost six successive home games - equalling a club record.
Pools striker Andy Monkhouse volleyed against the crossbar from just outside the area after 21 minutes. Four minutes later, the visitors nabbed the only goal.
Yeovil could have been out of sight by the break. Andrew Williams had an effort ruled out for offside and the striker turned Peter Hartley on the edge of the area only to smash high over the bar.
Pools' half-time substitute Adam Boyd tried to lob goalkeeper Rene Gilmartin from distance but could only lift the ball into his hands, and Monkhouse had a half-chance but got the ball stuck between his feet. In injury time, Nathan Luscombe fired against the woodwork for the home side.