Cyanobacteria are important natural sources of biomolecules and active compounds with promising biological activities against a wide range of microbial pathogens. The study aimed to evaluate the chemical composition and antibacterial activities of colony-forming cyanobacteria, Desmonostoc muscorum. Proximate analysis showed that D. muscorum biomass possesses high concentration of carbohydrates (35.50 ± 0.12%), protein (20.19 ± 0.03%), and ash (16.90 ± 0.02%). The elemental composition of D. muscorum biomass is in a decreasing order of Ca > Mn > Mg > K > Na > Fe> Zn > Cr > Pb > Cu > Cd. Also, D. muscorum extract exhibited potent antibacterial activities against Staphylococcus saprophyticus, Methicillin-Resistant Staphylococcus aureus, and Listeria monocytogenes with MIC values of 125 μg/mL, 125 μg/mL, and 250 μg/mL, respectively. The current study documents the promising use of D. muscorum as good sources of microelements and compounds which can be harness for food and medical applications.