The small penaeid shrimp Metapenaeopsis goodei (Smith, 1885) is widely distributed along the Atlantic Ocean, yet information on its morphometric features is scarce or non-existent. This study evaluated differences in the morphometric relationships between sexes of juvenile (carapace length mean: 6.8 mm, range: 3 to 10.5 mm) in a nursery ground of northeastern Yucatan peninsula, Mexico. The morphological features studied were carapace length (CL), total length (TL), rostrum length (RL), relative rostrum length (RL∕CL ratio), and total wet weight (W). About 19% of females ( n = 207 ) and 54% of males ( n = 167 ) had size classes of complete sexual maturity reported for this species, i.e., >8 and >6 mm CL, respectively. Analysis of covariance detected significant differences between sexes for the TL-CL, RL-CL, RL/CL-CL and CL-W relationships. The coefficient b (slope) of the morphometric relationships decreased about 4 to 20% in females relative to males. The TL-CL, RL-CL and CL-W relationships showed positive allometry for both sexes, but more strongly in males, suggesting that as juveniles increase in CL the males become larger, heavier, and with longer rostrum than females, although males did not reach the same maximum mean CL as females. The positive allometric growth for the CL-W relationship suggests that weight increases more than length, probably because of the abundant food supply on the nursery ground. Results from the current study indicate that separation of morphometric relationships for females and males is necessary for M. goodei that inhabit nursery grounds. Sexual dimorphism in morphometry appears to reflect development to sexual maturity of juveniles in shallow inshore nursery grounds, before migrating to offshore adult habitats.