Abstract: Cucurbit seeds are commonly consumed in Niger. In previous studies we determined the protein, fat, minerals, fatty acids, tocopherols and β-carotene contents. The aim of this study was to determine the polyphenol, total flavonoids, condensed tannins contents and the antioxidant capacity of the seeds of the 17 varieties of L. siceraria species and a single variety of C. colocynthis belonging to the Cucurbitaceae family. The variance analysis showed a very significant difference between the varieties for the parameters studied. Indeed, in all of the seeds, the results showed the existence of an antioxidant activity that vary from 3.7-114 μmol EAA/100 g. The phytochemical screening showed fluctuating levels of phenolics from 79.2-203 mg/100 g, flavonoids from 0.08-17.9 mg kg-1 and tannins from 0.05-1 mg kg-1. There is a positive correlation between the antioxidant activity and the polyphenol content (r = 0.79) on the one hand and on the other hand between the polyphenol and flavonoids content (r = 0.76). This study on Cucurbitaceae seeds, highlights their biological potentialities and can therefore contribute to the fight against proliferative diseases such as (type 2 diabetes and hypertension) in Niger.