Mr. Gregory Devlin is a history teacher at Ridgeway School. He is known for being very strict to his students, even in his former position as the lunchroom monitor and gave Spencer detention for playing with his fruit. He also hates 3-hole punched paper, as revealed to Carly in the episode iPromise Not to Tell, when he keeps Carly from getting straight A's by giving her a B+ on a history paper. He also talks very fast, so it is very hard for students to keep up with him when taking notes.

He also appeared in iKiss, where he told Freddie, loudly, to be proud of himself for never having his first kiss. However, this backfired when everyone started laughing at Mr. Devlin. He was last seen shouting at the crowd of students laughing at Freddie.

Mr. Devlin was portrayed by Adrian Neil.