Walnut male flowers (WMFs) are important by-products of walnut production. Studies on the nutritional quality of WMFs have predominantly focused on a single variety or region, and scientific information on different varieties is limited. In this study, ten walnut male flower (WMF) samples were evaluated and compared to assess their nutritional composition, bioactive contents, and antioxidant capacity. All WMF varieties were rich in protein, minerals, and amino acids, with leucine being the most abundant amino acid. All varieties exhibited low fat content and a favorable Na/K ratio. Additionally, they contained high levels of polyphenols and flavonoids, which were associated with strong antioxidant capacity. The variety seemed to exert a greater influence than the region on the nutritional composition and bioactive contents of WMFs. Moreover, polysaccharide, starch, soluble sugar, polyphenol, and fat might serve as potential markers for distinguishing different WMF varieties. This study provides a reference for the development and utilization of WMFs.