Trevor appeared again in ''[[XY125|A League of His Own!]]'', in which he was revealed to have fulfilled the requirements to enter the [[Lumiose Conference]]. In the opening of the conference, he and Tierno were seen talking to Ash. The next day, he battled [[Alain]] in the first round and lost without [[Fainting|knocking out]] any of his Pokémon, leaving Trevor disappointed in himself. After losing, he decided to remain in Lumiose City to watch the rest of the League together with his friends, which he did up until ''[[XY131|Down to the Fiery Finish!]]''.
He reappeared in [[XY132]], where he joined the fight against [[Team Flare]].
He reappeared in [[XY133]], [[XY135]], and [[XY136]].