As a screenwriter and performer he has contributed to many local television shows, including Wellington Paranormal, and feature films Pork Pie and Loop Track.

[1][6] Sainsbury was encouraged in acting and drama by his parents, including at age 9, accompanying them to the Matamata Operatic Society rendition of Little Shop of Horrors.

He has produced over 50 plays and several of them, including And Then You Die, The Christmas Monologues, The Mall, Loser, A Simple Procedure and Sunday Roast have been performed internationally.

[1][9] Sainsbury has written many New Zealand web series and comedy shows, including International Emmy Awards winner INSiDE.

[12] He also starred in Pork Pie and appeared in local shows including Jono and Ben, 7 Days, Spinal Destination, Snack Masters, Have you been Paying Attention?, Give Us a Clue, Under the Vines, Educators, Taskmaster New Zealand and Wellington Paranormal.

He has written, co-written and performed in multiple live comedy theatre shows including The Opening Night Before Christmas, Infectious, Camping, D.O.C.ing, Giggly Gerties, Dynamotion, Gays in Space, and Hauraki Horror.

[27] Sainsbury released a fictional comedy murder mystery podcast series called Small Town Scandal that was produced and distributed by New Zealand Media and Entertainment in 2023.