Monday night's game pitted fourth-bottom Osasuna against last-placed Levante, featuring Socceroos goalkeeper Maty Ryan.
The home side controlled the game from the kick-off, with Garcia in commanding form against the club where he played much of his career.
It was his cross from the right that brought Osasuna the lead after 13 minutes, Victor Munoz expertly heading down and into the net.
Garcia was fortunate 23 minutes later when he got his name on the scoresheet. His shot from just outside the box was cruelly deflected past Levante's Australian keeper Ryan.
Garcia refused to celebrate but acknowledged it was a vital win for his side.
"I'd have preferred it not to be against Levante, but I have to be happy because of what we were playing for," said Garcia.
"(These three points) feel necessary."
After the break, Ryan pulled off three quickfire saves in the 50th minute and then spread himself brilliantly to keep the scoreline down with his left foot in the 56th - to the astonishment of home fans.
Osasuna (15 points) are up to 15th in the 20-team table, three points clear of the drop zone, while Levante have nine points.
With AAP.
