Currently, nanotechnology is developing at an exponential rate because of its widespread applications in various fields of life sciences. Traditionally, nanoparticles are fabricated through a variety of physical and chemical approaches but because of their limited efficiency in biomedical applications, biogenic synthesis of nanoparticles has gained much attention. Biogenically fabricated magnesium oxide nanoparticles (MgONPs) possess unique features that enabled their use in therapeutics and environmental biotechnology. Biogenically MgONPs can be fabricated using plant extracts (Manihot esculenta, Rhizophora lamarckii, Ocimum sanctum, rosemary, Bauhinia purpurea, and others), bacteria (S. coelicolor, A. johnsonii RTN), fungi (Aspergillus flavus TFR‐12, Aspergillus brasiliensis TFR 2, white‐button mushroom's) and algae (S. whigti). These biogenically synthesized MgONPs are being reported as antifungal, antioxidant, antibacterial, antipyretic, anti‐inflammatory, and anticancer agents. Moreover, their photocatalytic activity is far being discovered against certain organic dyes. This review focuses on the biogenic synthesis of MgONPs, their applications in therapeutics, and as antimicrobial agents as well as future prospects associated with their applications in the biomedical field.