Investigating the time activity budgets of fiddler crabs is very important to determine the effects of sex and body size on allocating time for different activities. Few previous studies investigated the effects of sex and body size on time allocations in underground mating species. This study determines the effects of sex, size and their interaction on time allocations in a surface mating species (Tubuca rosea (Tweedie, 1937)). The surface activities of large and small, male and female crabs were video recorded. Afterwards time allocations for various activities (e.g., feeding, standing (vigilance), walking, inside burrows, grooming, burrowing, mating, and for males only, fighting and claw-waving) were calculated. All crabs spent most of their time on feeding than on other activities. Smaller crabs spent more time being vigilant, whereas larger crabs spent more time on courtship displays (grooming, and waving), and fighting. Between sexes, females spent more time standing, but less time on walking and grooming than males. Predation risk, reproductive maturation, breeding/non-breeding season, and energy conservation could be important factors for shaping time allocations in T. rosea.