Lagenidium giganteum is a water mold and an effective mosquito control agent with limited use due to poor survival and contamination during storage. Invert extracellular metabolites of L. giganteum is easy to produce, long shelf life, and a potential candidate in tropical climates. This fungus was grown in PYG broth in the laboratory at 25 ± 2°C, and relative humidity was maintained at 75 ± 5% for 15 ± 2 days. Filtration process of metabolites was done using Whatman filter paper, column chromatograph, and range syringe filters techniques. Then 5-ml fractions were collected and used to assay larvicidal efficacies. Larvicidal efficacies were performed against Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti at five different concentrations, viz. 1.68, 1.99, 2.17, 2.30, and 2.40 ppm. And also, filtrates were assessed against four species of nontarget organisms named Daphnia pulex, Cyclopes, Lymnea auriculeta, and tadpoles of Rana tigrina with different concentrations. The mortality values were subjected by the Probit analysis. The complete mortalities that resulted from applying filtrates dosage on all instars of mosquitoes persisted for a period of 24, 48, and 72 h, respectively. The efficacies in killing instar of three important vectors and safer for nontarget organisms with good biological stability of extracellular metabolites make this a promising alternative to mycelium and conidial-based larvicides. It could be regarded as fungal-based natural larvicide for the use of vector control.