Reviews of "Before I Go to Sleep" are generally unfavorable. As of 2015, critic review aggregator RottenTomatoes.com rates the film as rotten, with only 35 percent of critics giving it positive reviews.
Critics accused "Before I Go to Sleep" of being lackluster, implausible and silly. Drew Taylor of The Playlist gave the film an "F" grade, saying that it was poorly plotted and didn't make sense. Rafer Guzman of Newsday was slightly less severe, acknowledging that the film had an interesting premise but that other films had covered similar territory with greater imagination. Other reviews, both negative and positive, praised the talents of stars Nicole Kidman, Colin Firth and Mark Strong.