Agro-industrial wastes (by-products) were used in a biphasic fermentation system for the optimal production of Metarhizium anisopliae conidia. Submerged fermentation carried out with 45 g L−1 glucose and 36 g L−1 yeast extract rendered the highest blastospores yield within four days. Blastospores were used as the inoculum source in solid-state fermentation alternatively to conidia suspension. The solid substrates included rice, bran, and inert supports for growth and sporulation. Pre-cooked rice inoculated with blastospores showed higher yield and faster conidia production compared to inoculation with conidia. The optimal conidia production was obtained after seven days when inoculated with blastospore-based pre-culture. Conidia production after fungal growth on wheat bran (1.2 × 109 conidia g−1) was twice as high as on corn bran. Sugarcane bagasse was the best supporting matrix for growth and sporulation (5.14 × 108 conidia g−1). This study highlights the feasibility of a cost-effective biphasic liquid-solid fermentation of M. anisopliae.