Background/Objectives: While cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) significantly improve the outcome of pseudomyxoma peritonei (PMP) patients, recurrence remains a concern, highlighting the need for careful patient selection. This systematic review and meta-analysis evaluated the clinical-pathological, (immuno-) histological, and molecular prognostic factors in PMP patients undergoing CRS and HIPEC. Methods: Databases including PubMed, MEDLINE, Cochrane library, Embase, Scopus, and Web of Science were searched up to July 2024. Studies assessing clinical-pathological, (immuno-) histological, and molecular parameters influencing overall, progression-free, and/or disease-free survival were included. Statistical analysis was performed using R (Version 4.4.3) with random-effect models employed to address heterogeneity. Subsequent subgroup analyses were conducted to investigate potential sources of publication bias (Egger test). Results: A total of 16 studies involving 4009 PMP patients were included. Age, sex (male), completeness of cytoreduction score, peritoneal cancer index, tumor markers (CEA, CA 19-9, CA-125), tumor grade (high), histological subtype, and Ki-67 were significantly associated with prognosis prediction. Conclusions: Despite the presence of heterogeneity and publication bias, clinical-pathological and (immuno-) histological parameters were significantly associated with prognosis in PMP. The findings highlight the importance of integrating clinical-pathological and (immuno-) histological parameters in the individualized multidisciplinary management of PMP patients undergoing CRS and HIPEC. Future research should focus on incorporating molecular and genetic biomarkers to further refine patient selection and improve treatment outcomes.