Reality Monitoring (RM) criteria has been proposed as a forensic tool in order to discern between perceived and imagined memories. However, no systematic evidence has been provided on its validity for use in testimony evaluation. Thus, a meta-analytic review was designed to study its validity in forensic setting. A total of 40 primary studies were found, yielding 251 effect sizes. Random-effects meta-analyses correcting the effect size for sampling error and criterion unreliability were performed. The results showed that the total RM score discriminated, d = 0.542 (δ = 0.562), between imagined and perceived memories of events. In relation to individual criteria, the results showed support for the model's predictions (more external attributes in perceived memories) for clarity, d = 0.361 (δ = 0.399), sensory information, d = 0.359 (δ = 0.397), spatial information, d = 0.250 (δ = 0.277), time information, d = 0.509 (δ = 0.563), reconstructability of the story, d = 0.441 (δ = 0.488), and realism, d = 0.420 (δ = 0.464), but not for affective information, d = 0.024 [-0.081, 0.129]. Nevertheless, except for temporal information, the results are not generalized (negative effects may be found). For cognitive operations, the results corroborated, although the magnitude of the effect was lower than small, the hypothesis (more cognitive operations in imagined memories), d =-0.107 [-0.178,-0.036] (δ =-0.119). The moderating effects of age (more cognitive operations on imagined memories in adults, and on perceived memories in underage), evocation type (external attributes discern between imagined and perceived memories, in both self-experienced and non-experimented accounts), and criteria score (the results varied by score) moderators were studied. As conclusions, forensic implications for the validity of the RM technique in court proceedings are discussed.