Sarconesia chlorogaster (Wiedemann) (Diptera: Calliphoridae) is an endemic blow fly species of forensic importance in South America, and whose duration of pupal development is about 70% of the total immature development time. Therefore, morphological changes during this stage, if refined, may provide greater accuracy and reliability in the calculation of minimum postmortem interval. Considering the importance of this species, the main objective of this work was to identify and describe temporal intrapuparial morphological changes of S. chlorogaster. The development of S. chlorogaster reared on an artificial diet and at two constant temperatures (20 and 25°C) was monitored. Every 8 h until the end of the pupal stage, 10 pupae were killed, fixed, and had their external morphology described and photographed. Of the 29 morphological characteristics described, 13 are potentially informative for estimating the age of S. chlorogaster. In general, body shape (presence or absence of tagmatization), general coloration, visible presence of the mouth hook (portion of the mandible), thoracic appendages, change in eye color, and bristle formation are the most useful characteristics for determining specific age. The results presented here make it possible to estimate the postmortem interval of a corpse using intrapuparial morphological characters, expanding one's ability to estimate postmortem interval.