Objective: Few studies have attempted to describe the range of cognitive impairments in individuals with psychiatric disorders who experienced maltreatment as children. The aims of this meta-analysis were to establish the impact of maltreatment and psychiatric disorders on cognition, and to examine the change in impact from childhood to adulthood. Method: Twelve publications from 1970 to 2013 were included, with the following inclusion criteria: (a) individuals with a psychiatric disorder who experienced maltreatment, (b) use of at least 1 standardized neuropsychological measure, and (c) use of a control group without any psychiatric disorder or mistreatment. The majority of studies (10/12) were about posttraumatic stress disorder. Several effect sizes were calculated (Hedge’s g) according to the cognitive domains. Results: The results of the meta-analysis demonstrate that the combination of psychiatric disorders and childhood maltreatment has a negative impact on global cognitive performance, with a moderate effect size (g = −0.59). The most affected cognitive domains for individuals aged 7- to 18-years-old were visual episodic memory (g = −0.97), executive functioning (g = −0.90), and intelligence (g = −0.68). For individuals over the age of 18-years-old, the most affected cognitive domains were verbal episodic memory (g = −0.77), visuospatial/problem solving (g = −0.73), and attention (g = −0.72). The impact of maltreatment and psychiatric disorders was greater in children than in adults (slope = 0.008, p < .002). Conclusion: The results suggest that exposure to maltreatment and the presence of psychiatric disorders have a broad impact on cognition, with specific neuropsychological profile.