mentalflossvideo is the YouTube show for the popular trivia magazine mental_floss. The channel was created in early 2013, and features weekly list videos (uploaded on Wednesday) by John, or occasionally by guests. At the end of every video John answers a mind blowing question asked by a commenter.

Two videos to date have been hosted by Hank (who filmed in Missoula and was digitally composited onto the Indianapolis set). Other guest hosts to date include Emily Graslie (thebrainscoop), Craig Benzine (Wheezy Waiter), Grace Helbig (DailyGrace), Hannah Hart (My Harto), and Derek Muller (Veritasium).

When introducing the channel on vlogbrothers, John implied that Quiz videos by Hank would also be frequently uploaded; to date, only one has been released.

John has a significant personal connection to the magazine, as it was the site of his first writing job; Hank had previously done significant work for the magazine as well.