The objective of this study is to document the presence of external morphological malformations in the blue swimming crab Portunus segnis (Forskal, 1775) (= Portunus pelagicus), from the Timsah Lake, Suez Canal. A total of 269 specimens were collected, out of which 28 individuals (19 males and 9 females, 7% and 3.4 % respectively) showed malformations with different percentages in chelipeds, swimming legs, carapace and abdomen. The presence of malformations was different between the sexes. In males, the malformations were observed principally in the chelipeds, while in females were in the chelipeds and swimming legs. The cause of the malformation could be related to wound healing processes after an injury or molting artifacts, and perhaps developmental disorders based on toxic substances.