In Ben 10: Alien Force, Max looks mostly the same, save for more wrinkles and a darker red shirt with whiter hair. In the episode Ben 10 Returns, he leaves a transmission for Ben, stating that he is investigating renewed alien activity on Earth and claims that he has the Omnitrix. An image of a DNAlien flickers at the end of the transmission. It is conceivable from this, that Max was wearing an ID-Mask and that the DNAlien in the teaser was actually Max (the voice of the DNAlien is confirmed as Paul Eiding), implicating himself as a mole to distract the Highbreed from Ben (whom, with the Omnitrix, poses a greater threat). The message was probably in code, telling Ben to put on the Omnitrix once more. An earlier theory suggested that the hologram might have been that of a DNAlien who wanted to keep Ben out of their business, but instead made a big mistake.
In the episode Max Out, Max destroys a Xenocyte hatchery by detonating a Null Void Projector, which after removing its focusing lens, makes a "pretty good imitation of a hand grenade" and produces an explosion that covers over half a mile wide. Max appeared to have been killed in the blast, but was instead sent to the Null Void (episode: Voided), where he, calling himself "The Wrench", fought Dr. Animo, who was calling himself "D'Void". He has since appeared in the two-part episode War of the Worlds to aid Ben in his battle with the Highbreed, along with the "Plumber Helpers". At the end, he takes on the Plumber kids who fought with Ben as his apprentices. He and the Plumber kids also appear in the two-part episode Vengeance of Vilgax.
In the episode If All Else Fails, it is revealed that the Highbreed had infected him with a dormant seed, which was part of a failsafe plan of the Highbreed. It is mistakenly activated by a Highbreed officer, who was unaware that the Highbreed has called-off the war. Max is freed from the seeds' control by Ben, Gwen, and Kevin. Also during the episode, he mentions he knew Kevin's father, Devin Levin.
In Above and Beyond, it is revealed by Pierce that Max is now the Earth's Magister (an equivalent to 'Colonel', likely assigned as Earth's Magister after the Highbreed conflict, during which the former Magister Labrid was killed). In the episode, Max set up a scenario in which Ben was to go on a rampage on board an orbiting Plumbers' space station. He then calls the Plumbers' Helpers to come and save him. They manage to defeat Ben, but the battle had caused the space station to fall out of orbit towards the city of London. The Plumbers' Helpers decide to activate the station's self-destruct, which would mean sacrificing their lives in the process. However, the space station doesn't explode. Instead, Max appears along with Ben, who reveals to the Plumbers' Helpers that the space station is a Plumber training facility and that Ben's "rampage" was set up to test them. Max also states that by putting "the safety of others ahead of their own lives", the Helpers will be admitted to Plumbers' Academy.
In the season finale, The Final Battle, Max takes part in the fight against Vilgax. When Kevin returns to his human form, Max states that the Omnitrix kept him in his mutated form. Max aids Gwen in trying to stop the ship from crashing into Bellwood. After Ben escapes from Vilgax, he, Gwen, and Kevin share a group hug with Max.