Needing a point to finish top, the Canaries picked up all three as the midfielder followed up his late equaliser at the Priestfield Stadium last September with a well-taken second-half opener at Carrow Road.
Defender Michael Nelson then headed home a corner to complete a rather flattering margin of victory for the hosts.
Gillingham might have taken the lead during that spell but striker Dennis Oli twice failed to convert when in one-on-one situations with goalkeeper Fraser Forster - and those misses were to prove costly.
Norwich then took charge and got the goal they needed in the 74th minute when Russell curled the ball over keeper Alan Julian from 25 yards, with the ball clearly going over the line before being headed clear by a defender.
Nelson completed the scoring eight minutes later as he rose highest to head home a Simon Lappin corner for his second goal in successive matches.