Objective: To describe the clinical characteristics and prognosis of chronic myelomonocytic leukemia (CMML) patients co-occurrent with lymphoid/plasma cell neoplasms (LP-CMML). Methods: We retrospectively identified nine LP-CMML cases who visited the First Affiliated Hospital of Nanjing Medical University between January 2016 and August 2025, and compared their features with de novo CMML(DN-CMML). Results: The median age of LP-CMML patients was 66(58,76) years, with 8(88.9%) being male. All patients were classified as CMML-1. The most common co-existing lymphoid/plasma cell neoplasm was diffuse large B-cell lymphoma(3 cases). No differences were found between LP-CMML and DN-CMML in basic clinical characteristics, cytogenetic risk stratification and disease risk stratification. Based on the sequence of occurrence, 4 patients were classified as therapy-related CMML (tCMML) and 5 as non-tCMML. Compared with the non-tCMML patients, tCMML patients were younger(P=0.016) and the dysplastic phenotype predominance(P=0.048). Dynamic monitoring of one tCMML patient revealed a pre-existing CMML precursor state at the time of lymphoid neoplasm diagnosis, with clonal evolution during the disease course. Survival analysis showed shorter median overall survivals(6 months vs. 40 months,P < 0.001) and median progression free survivals(5 months vs. 29 months,P < 0.001) for LP-CMML than those of DN-CMML. No difference was found in survivals between tCMML and non-tCMML subgroups. Conclusion: LP-CMML indicates clinical heterogeneity and poor survival.