The global demand for crabs, coupled with increasing threats to natural populations, creates the need to investigate captive breeding programs. To achieve this, it is crucial to acquire a comprehensive understanding of key aspects of their life cycle. This study represents the early comprehensive characterization of the red mangrove crab, Ucides occidentalis. Furthermore, leveraging epifluorescent microscopy, we examined the effect of six distinct microalgae diets on the progression of larval stages and their subsequent survival. Embryonic development in U. occidentalis unfolded over a period of 14 days, systematically detailed across eight distinct phases, each marked by the progressive emergence of the embryo and its associated appendages. Notably, an increase in the heart rate was registered just prior to spawning. Following spawning, a brief period of 10–15 min elapsed before the embryos successfully ruptured the chorion. Larval development underwent segmentation into five zoeal stages (zI–zV), spanning a 15-day duration, with an equivalent temporal period encompassing the megalopal stage until the attainment of the first juvenile crablet. Each transition between stages was heralded by a molting event. Despite our observations confirming the ingestion and digestion of the assessed microalgae, it became evident that diet supplementation with rotifers and brine shrimp is essential to optimize molting periods and, consequently, enhance survival rates. Specifically, diatoms Chaetoceros gracilis and Chaetoceros muelleri were ingested and digested up to the zoea V stage. In contrast, the microalgae Tetraselmis maculata and Rhodomonas salina, while undergoing ingestion and digestion, were only able to sustain larvae until the zoea III stage. The outcomes of our research affirm the viability of U. occidentalis crablet production within a laboratory setting, thereby offering the potential inclusion of this species as a valuable aquaculture product. This endeavor holds the promise of contributing to the conservation and enhancement of wild U. occidentalis populations.