The essential oil composition of an endemic Algerian Cruciferae, Pseudocytisus integrifolius (Salisb.) Rehder, was analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). Eighty-three components representing more than 96.5% of the oil were identified. The major components were dimethyl disulfide (33.4%), dimethyl trisulfide (24.2%), and an unsaturated nitrile (31.7%). Fractionation on a silica gel column led to the identification of trace-level compounds, in particular, polar compounds such as nitriles and aldehydes, and to the isolation of dimethyl disulfide, dimethyl trisulfide, and an unsaturated nitrile. Structural analysis using high-resolution mass spectrometry (HRMS) and 1H,13C NMR techniques enabled the identification of pent-4-enenitrile. Variation in essential oil composition and yields was studied according to harvesting time, drying, and parts of the plant. The essential oil of aerial parts was tested for its antibacterial activity using a paper disk method. The oil was effective on the inactivation of Escherichia coli and Pseudomonas aeruginosa and ineffective on the inactivation of Staphylococcus aureus.