<p>Juvenile red mangroves (Rhizophora spp) play a critical role in early-stage biomass accumulation, which directly contributes to carbon sequestration. However, species- and age-specific allometric models for this growth phase are scarce. This paper developed site- and age specific allometric equations to estimate aboveground biomass (AGB) and belowground biomass (BGB) of approximately 1-year old <i>Rhizophora mangle</i>. Sixty representative seedlings were destructively sampled randomly based on the mean size-class distribution within the revegetated area. Due to observed structural variability, segmented regression was fitted; and thresholds of height and collar diameter were used to stratify the dataset into two subsets. The seedlings were carefully uprooted, separated into AGB and BGB components; freshly weighed, and oven-dried until a constant weight was achieved, to obtain dry biomass. Candidate equations were fitted for AGB and BGB, utilizing power-law models and log-transformed variables. The models were validated with leave-one-out cross-validation (LOOCV). The best fit equations utilized both height and diameter as predictor variables, and the predictive power of the equations were high (R² &gt; 0.80, RMSE &lt; 0.39) with no significant difference between the observed and predicted AGB and BGB. The developed models offer an efficient and non-destructive method of estimating total biomass of juvenile mangroves, which has a direct effect on the restoration monitoring, blue carbon evaluation, and ecological surveillance of mangrove ecosystems. This enables performance evaluation of restoration initiatives and provide baseline for long-term monitoring and understanding of biomass accumulation and dynamics in red mangrove ecosystem.</p>