Gambhir, who had been woefully out of form for long, notched up a superlative century in 195 balls while India A captain Cheteshwar Pujara was giving him company on 82 as the hosts went to tea at 208 for one on the second day at the KSCA Stadium.
Seeking to make a comeback to the senior team, Gambhir was batting on 115 off 210 balls and had hit 11 boundaries before going for the break.
Gambhir, who is playing his 148th first-class match, has so far batted for 275 minutes, as India A trailed by just 60 runs with as many as nine first-innings wickets remaining.
The Delhi left-hander, who seemed determined to play a long innings in his quest to force the national selectors to sit up and take note, stroked his way to his 35th first-class century by flicking spinner Nikita Miller for a boundary.
The opener showed glimpses of his old self, mixing aggression with defence as per the situation. Gambhir was flamboyant in the morning session when he cracked eight scintillating fours, but looked guarded in the second as he did not score a single boundary.
Most of his runs after lunch came in singles and twos, reflecting his determination not to fish at any away-going balls, which the West Indian A bowlers had offered to him in plenty.
Gambhir got good support from Pujara, who scored his runs after batting watchfully for over three hours and hitting nine exquisite boundaries.
Both have been involved in an unbeaten second-wicket stand of 173 runs. Resuming at their overnight score of 10 for one, India had a poor start to the day as they lost opener V A Jagadeesh early when he was castled by Trinidadian left-arm fast bowler Delorn Johnson for 16.