One oil sample isolated from aerial parts of Pulicaria mauritanica Coss. from Western Algeria has been analyzed by GC(RI), GC-MS and ¹³C NMR. In total, 21 components, accounting for 97.0% of the oil, were identified. Then, 36 oil samples coming from plants harvested at two flowering periods in three locations were analyzed by GC(RI) and ¹³C NMR. Although all the oil samples exhibited similar composition, dominated by carvotanacetone (89.2-96.1%), the yield of essential oil varied drastically from sample to sample (0.35-1.44%), depending on the location of harvest. The essential oil displayed moderate antimicrobial effect against bacteria, yeast and filamentous fungi (MIC = 2-4 µL/mL).