This study aimed to evaluate the efficacy and safety of lumateperone in treating bipolar disorder and schizophrenia. A comprehensive literature search was conducted across multiple databases and websites from inception to July 16, 2024, to identify both published and unpublished randomized controlled trials (RCTs). Meta-analyses were performed using random-effects or fixed-effects models depending on statistical heterogeneity. Relative risks (RRs) or standardized mean differences (SMDs) with 95% confidence intervals (CIs) were used to summarize the effects. Out of 931 records screened, seven RCTs (four focusing on bipolar depression and three on schizophrenia) were eligible for inclusion. Lumateperone was efficacious in reducing depressive symptoms in bipolar depression (SMDs = -0.36, 95% CI: -0.59 to -0.13). In treating schizophrenia, lumateperone exhibited a lower combined SMD of -0.14 (95% CI: -0.27 to 0, P = 0.051, I² = 49.6%), showing no significant difference from the placebo group, although the p-value approached significance. The lumateperone group showed significantly higher response rates compared to placebo in both bipolar depression (RRs = 1.27, 95% CI: 1.07 to 1.51) and schizophrenia (RRs = 1.44, 95% CI: 1.12 to 1.86). Common treatment-emergent adverse events included somnolence, dry mouth, dizziness, nausea, and headache (RRs = 1.30 to 3.29). Importantly, lumateperone did not significantly increase extrapyramidal symptoms (EPS, RRs = 1.46, 95% CI: 0.84 to 2.53). Lumateperone is effective in treating bipolar depression but does not significantly reduce symptom severity in schizophrenia. It has a favorable safety and tolerability profile. However, caution is warranted in interpreting these findings due to the limited number of studies included.