On review aggregator Rotten Tomatoes, the film holds an approval rating of 94% based on 36 reviews, with an average rating of 7.1/10. The website's critics consensus reads, "Led by first-rate performances from its stars, My Little Sister explores familial bonds and terminal illness with honesty and sensitivity".[5] On Metacritic, the film has a weighted average score of 75 out of 100, based on 13 critics, indicating "generally favorable reviews".[6]
Peter Bradshaw of The Guardian called My Little Sister a "fierce and fraught family drama",[7] while Wendy Ide of The Observer called the film a "terrific, prickly sibling drama".[8]
Ty Burr of The Boston Globe called the film "a bracing trip", and "a work of daredevil nerve that serves as its own reward".[9]
According to Anna Smith of Deadline Hollywood, the film is "moving without being mawkish".[10]
