Several papers have suggested that the Freshwater Cichlid Crenicara punctulata is capable of protogynous sex change. These studies provide behavioral data and descriptive details of external morphology but lack information about gonadal histology, which is essential for definitive evidence of sequential hermaphroditism. Therefore, this study was designed to determine whether C. punctulata is a sequential hermaphrodite. The present study included a behavioral experiment, an isolation/transformation experiment, as well as a detailed analysis of gonadal structure. The behavioral experiment established social hierarchies in four groups of juvenile female C. punctulata. The hypothesis that the dominant female in each group would be the only individual to develop male secondary sexual characteristics in that group was verified. The isolation experiment tested the hypothesis that female C. punctulata would change sex without the presence of conspecifics. After social isolation, females that were previously dominant among a group of females in a male harem developed male secondary sexual characteristics. Histological analysis revealed that these individuals possessed testes, whereas all dominant females examined possessed mature ovaries. The results from behavioral, isolation, and histological portions of this project strongly suggest that C. punctulata is a protogynous sequential hermaphrodite, at least in captivity.