Forest ecosystems are vital to global carbon cycling as sinks or sources, while fast-growing, adaptable pines such as P. kesiya and P. oocarpa are central to national carbon sequestration efforts. This study was aimed at determining biomass accumulation variations and carbon stock dynamics between these two species at the age of 16 years in the Viphya Plantations, a prominent timber producing area in northern Malawi. Following the systematic sampling, forest inventory data was collected from 20 circular plots of 0.05 ha each. Above and below ground biomass was estimated using generic allometric models for pine species. Findings indicate that there were significant (P<0.001) differences in biomass accumulation and carbon sequestration between P. oocarpa and P. kesiya plantations. P. oocarpa accumulated more biomass (298.86±12.09 Mgha^-1) than P. kesiya (160.13±23.79 Mgha^-1). Furthermore, P. oocarpa plantation had a higher annual carbon sequestration (32.22±1.30 tCO₂e/ha/yr) as compared to P. kesiya plantation (17.26±2.56 tCO₂e/ha/yr). In addition, the uncertainty was less than 1% and fit within the IPCC’s recommended range (<15%). Therefore, the study has demonstrated that species selection should match management objectives: P. oocarpa maximizes short-to-medium term carbon sequestration and productivity, while P. kesiya supports long-term soil carbon stability. Hence, integrating both optimizes carbon benefits.