Martins only formalised his move to Levante on Friday after being allowed to leave Rubin Kazan, and repaid his new employers’ faith with a goal just 41 minutes after entering the action as a half-time substitute.
David Zurutuza had earlier handed visiting Sociedad a first-half lead that they held until the 70th minute when Jose Barkero levelled from the penalty spot.
With the clock ticking down Martins pounced inside the area to lift Levante to their second win of the season and a place inside the top 10.
The hosts were hugely unlucky not to be in front when Barkero unleashed an effort from inside the area that cannoned back of the post.
Sociedad threatened in the 18th minute when Carlos Vela curled an effort over from distance, and five minutes later the visitors were in front when Zurutuza picked up the ball on the edge of the area and powered a low drive into the bottom-right corner.
Juanlu’s curling effort forced a good save from Claudio Bravo as Levante went in search of an equaliser, but in truth the hosts looked short of ideas up front and it was no surprise to see coach Juan Ignacio Martinez introduce Martins for Vincente Iborra at the break.