In recent years, psychological interventions have been used to alleviate internalized stigma in people with schizophrenia spectrum disorders, but outcomes have been inconsistent. The aim of this review was to examine the existing evidence regarding this matter. Four electronic databases (EMBASE, MEDLINE, PsycINFO, and the Cochrane Central Register of Controlled Trials) were searched from inception until 8 September 2022, using appropriate strategies. The eligibility, quality, and strength of evidence of each study were all evaluated against the predetermined standards. Further quantitative analyses were performed using the RevMan software. A total of 27 studies were included in the systematic review. Eighteen studies with extractable data for meta-analysis yielded a statistically significant overall effect (Z = 3.00; p = 0.003; 95% CI: −0.69 [−1.15, −0.24]; n = 1633), although there was considerable heterogeneity (Tau2 = 0.89; Chi2 = 303.62, df = 17; p < 0.00001; I2 = 94%). Subgroup analyses for Narrative Enhancement and Cognitive Therapy (NECT) produced a statistically significant and highly homogenous effect (Z = 3.40; p = 0.0007; 95% CI: −0.44 [−0.70, −0.19]; n = 241; Tau2 = 0.00; Chi2 = 0.14, df = 2 (p = 0.93); I2 = 0%). In conclusion, the majority of the psychological interventions are successful in lowering levels of internalized stigma, especially NECT, and interventions that integrate multiple therapies may be more beneficial.