ABSTRACT The density and population parameters of the sea cucumber Isostichopus badionotus from Sisal, Yucatan, Mexico were determined during the fishing season. Belt transects of 200 m2 were set in 10 sampling sites at two fishing areas. All organisms within the belt were counted and collected. In the harbor, 7,618 sea cucumbers were measured and weighed: the population parameters were determined using FISAT II. Mean densities of I. badionotus in April 2011, September 2011 and February 2012 were 0.84 ± 0.40, 0.51 ± 0.46, and 0.32 ± 0.17 ind m-2, respectively. Sea cucumber total length varied from 90 to 420 mm, with a uni-modal distribution. The growth parameters were: L∞ = 403 mm, K = 0.25, and to = −0.18, with an allometric growth (W = 2.81L1.781). The total mortality was 0.88, whereas natural mortality was 0.38, fish mortality was 0.50 and the exploitation rate 0.54. Even when sea cucumbers fishery in Sisal is recent and in development with a high density (5570 ind ha−1), it is necessary to establish management strategies to protect the resource, such as an annual catch quota, catching size (>280 mm length), monitoring of population density, and reproduction and larval distribution.