The Philippines, being a tropical country in the Pacific, has long been culturing mussels for business and food consumption. However, they cannot determine at a glance what gender is which. This study is conducted to determine the difference of the male P. viridis and the female P. viridis through landmark based Geometric-Morphometric method. The population sample of P. viridis were obtained from Bula, General Santos City and was analyzed using the Rohlf’s Tps series. This software helps in comparing the two landmark-defined shapes of P. viridis. Nine homologous points were plotted: (1) Umbo, (2) Ligament, (3) Posterior Adductor 1, (4) Posterior Adductor 2, (5) Posterior Adductor 3, (6) Posterior Adductor 4, (7) Posterior border, (8) Projection and (9) Anterior Adductor to determine the difference of shell size of male and female P. viridis. This study focuses on relationships between length-width and length-breadth through relative warps and on the abundance of both sexes among the specimen. The value of significance is 1 (p > 0.05) therefore, it is significant and there is a difference on the shell shape. The discriminant function analysis also showed that p = 1, therefore there is a significant difference in the shapes of both sexes. Results show that male P. viridis shell have a total variation of 89.56%, basing from the six relative warps, compared to that of the female P. viridis which is 90.65%, with a slight variation at the ligament and posterior adductor border regions. Relative warps also show that female mussels are wider and bigger than male mussels. It is suggested that the observation of the green mussel shells are done within one area only so as to prevent misleading inputs and have certainty on the report between male and female mussel shell comparison done on only one species.