Caridean shrimp exhibit a wide variety of sexual and mating systems, and many species are well studied. Gnathophylloides mineri Schmitt, 1933 is a small, circumtropical symbiont of various species of sea urchins. Very little is known about the reproductive ecology of this species. Field surveys of a Jamaican G. mineri population showed that the reproduction occurred throughout the year, with a consistently high (>80%) percentage of ovigerous females in all seasons. The female: male sex ratio (1.31 : 1) was not significantly different than 1:1. Typically 1 to 3, and no more than 5, shrimp per urchin were observed at our field sites, a lower density than at other Caribbean locations where larger urchins support greater numbers of smaller individual shrimp. Gnathophylloides mineri Schmitt, 1933 occurred predominantly as pairs, and 85% of those pairs consisted of one male and one female. Such strong pair-bonding suggests the shrimp may be socially monogamous, unlike polygynous populations elsewhere that have greater numbers of shrimp per urchin and highly femalebiased sex ratios. The duration and fidelity of the pair bond in Jamaican G. mineri, however, is uncertain. Despite the high incidence of heterosexual pair-bonding, 74% of females with no male partners were ovigerous, suggesting that males engage in either extra-pair mating behavior or sequential monogamy. Given the circumtropical distribution and ecological variability among populations of G. mineri, the study of this species can provide valuable insight into the accuracy of current caridean reproductive models.