Abstract: Citrullus colocynthis and Citrullus vulgaris both look alike and belong to the genus Citrullus except that Citrullus colocynthis has thick black ring round its circumference. However, they are among the underutilized seeds of the World. Citrullus colocynthis and Citrullus vulgaris seed flours were analyzed for their amino acid and proximate compositions which was further subjected to statistical analysis to determine the correlation between the proximate compositions of the two species. The seeds show significant difference in fat and protein contents, but they are both good sources of fats and protein with values (56.00 and 49.59) % fat and (24.37 and 32.96)% protein contents for Citrullus colocynthis and Citrullus vulgaris respectively. However, they are closely related in fibre (1.91 and 2.00)%, moisture (3.08 and 2.75)% and ash contents (3.15 and 3.53)% respectively. The percentage essential amino acids of the seeds are also closely related: Citrullus colocynthis (52.73) and Citrullus vulgaris (50.86). The biological values of Citrullus colocynthis and Citrullus vulgaris are significantly different (12.83 and 26.35) with Protein efficiency ratios that are closely related (2.71 and 2.58) respectively.