Groundnut is one of the most important cash crops in Adamawa state, Nigeria. The ground nut is a good source of nutrients for humans, and the leaves and haulms are rich in nutrients for animal feed. Sclerotium rolfsii is a fungal that significantly constrains ground nut production by reducing yield and quality. This research aims to investigate garlic flower extract on the groundnut stem rot pathogen. The phytochemical analysis of the garlic flower extract, isolation of pathogen responsible for groundnut stem rot and determining the yield of the groundnut after treatment for 13 weeks. The qualitative phytochemical shows the presence of alkaloids, anthraquinones, flavonoids, glycosides, phenols, steroids, and terpenoids, while saponins and tannins were not detected. The flower contains high alkaloids with 5.04 ± 0.01, moderate terpenoids, glucosides, flavonoids, and phenols with 3.33 ± 0.03, 2.51 ± 0.04, 2.03 ± 0.01, 2.08 ± 0.02 respectively. The Sclerotium rolfsii was isolated from the stem rot of groundnuts. Treatment with the garlic flower extract significantly improved the yield of the groundnut. Therefore, the garlic flower can manage Sclerotium rolfsii.