two weeks into the new season, on 25 august 2011, mahon signed for league one side notts county on an initial pay-as-you-play deal. he made his debut for the club two days later as notts county lost 2–0 away to preston north end. mahon impressed during his first month with the club, and stated manager martin allen wished to secure a longer deal for the player — "the manager called me a few weeks ago and said he'd like to try to extend the deal to the end of the season". in october 2011, mahon signed an 18-month contract, keeping him contracted to the club until the summer of 2013. he was described as a "pivotal" player in notts county's season, and went on to make 34 appearances as county narrowly missed out on a play-off place on goal difference.<ref name="games played by gavin mahon in 2011/2012"></ref> at the end of the season, notts county announced that they wished to retain mahon's services, and the player was offered a new one-year contract, which he signed in june 2012.