Mae Greg Heffley yn ddisgybl newydd ac yn sylweddoli bod bechgyn lliprynnaidd eraill yn yr ysgol yn gorfod rhannu coridor gyda phlant mawr, cas sydd eisoes wedi dechrau siafio! Er mwyn ymddangos yn fwy aeddfed, mae Greg yn gwneud defnydd o Rowley, bachgen nad yw'n cael ei gyfri'n c??l Addasiad o Diary of a Wimpy Kid [Greg Heffley finds himself thrust into a new year and a new school where undersize weaklings share the corridor with kids who are taller, meaner and already shaving! Desperate to prove his new found maturity, which only going up a grade can bring, Greg is happy to have his not-so-cool sidekick, Rowley, along for the ride Adaptation of Diary of a Wimpy Kid]