Spot-tail mantis shrimp, is a marine crustacean belonging to the Family Squillidae and a member of the genus-Squilla. Mantis shrimps are so called because the second pair of limbs are greatly enlarged and shaped like the large grasping forelimbs of the praying mantis (an insect). The physico-chemical parameters of the water samples from the study site were measured in-situ and recorded. Samples of Squilla mantis were collected monthly between April and September, 2019. The size composition and growth pattern, length weight relationship, food composition and the reproductive biology of Squilla mantis were examined for a period of 6 months. The physico-chemical parameters of water samples collected from the Lagos Lagoon indicated that the condition of the lagoon was conducive to the aquatic organisms inhabiting it. S. mantis Total Length (TL) ranged between 7.3 and 15.0 cm, Carapace Length (CL)-1.4-4.0 cm and Total Weight (TW)-3.0-30.0 g. The length-weight relationship of the species exhibited a negative allometric (b< 3) growth. The coefficient of determination (R2) value for S. mantis was 0.2771, it showed a weak and negative growth pattern. The condition factor (K) for the combined sexes of S. mantis ranged from 0.9-1.5. The stomach contents were made up fish parts (17.0%), worms (19.0%), molluscs (oysters/squids)(6.0%), Crustaceans (small crabs and shrimps),(3.0), some unidentified food masses (1.0) and detrital organisms (5.0%). The food composition showed that S. mantis is a predatory species. The sex ratio (male: female) for S. mantis was 1: 0.38 and there was significant difference (P< 0.05) in the sex ratio. The fecundity estimated ranged between 225 and 1960 eggs with a mean of 318.36 eggs. There was a strong and positive correlation (r> 0.5) between fecundity and total length, fecundity and body weight (r> 0.5) for S. mantis from the lagoon. The study provided a baseline information and an addition to knowledge on Mantis Shrimp for fisheries management, taxonomist and for the population monitoring.