In order to establish a diagnosis of autism spectrum disorder (ASD), assessment by different informants is required. Sometimes, however, there are certain discrepancies between evaluators. With the aim of shedding light on possible discrepancies between informants, this work includes an updated review of the literature to examine the degree of agreement between different informants regarding the characteristic symptomatology of ASD in children and adolescents (up to 17 years of age). A total of 20 studies were analyzed, in which the levels of correlation between the evaluations carried out by different informants were moderate or low. A large part of the studies included in this review found that a greater degree of agreement among informants was associated with lower symptoms, a higher IQ, and better results in cognitive and adaptive skills. Considering these results, it is necessary to continue investigating contextual aspects that may be conditioning the results of multi-informant evaluations.