The Manicou or mountain crab, Eudaniela garmani (Pseudothelphusidae), is a freshwater land crab found at high elevations in the forests of Trinidad, Tobago, Margarita, and Eastern Venezuela. Anecdotal data suggest that the Manicou crab reaches sexual maturity at an unusually large size, and, by implication, at a relatively old age. Therefore, management and harvesting of this species need to be informed by accurate determination of the size and estimated age at maturity. Laboratory growth increment and intermoult period data were used to estimate the time for both sexes to mature. Breakpoint analyses and analyses of covariance (ANCOVA) of field-collected data were used to determine male and female morphometric or structural maturity while gross and histological examinations of ovaries were used to determine the size of onset of female sexual maturity. Morphometric maturity was initiated at about 42 and 47 mm carapace width (CW) in female and male crabs, respectively. Female morphometric or structural maturation ceased at about 67 mm CW, about the same size as the onset of female functional maturity (69 mm CW). It is estimated that female crabs attained functional maturity at about 3 years. A minimum capture size is thus recommended between 75 and 80 mm CW for female crabs. Patterns of allometric growth in the major propodus of males and the pleon width in females may be related to territorial and/or courtship behaviour in males and the use of the pleon as an incubation chamber in females.