This study aims to analyze the composition of essential oils of Murraya paniculata L. leaves over four-season cycles using GC-MS to investigate the effect of climate variation on the chemical composition as well as on their activities. The yield of the oil obtained by hydrodistillation ranged from 0.02% to 0.1% v/w; being the highest in spring and the lowest in summer. GC-MS identified a total of thirty-five components in the oil samples collected during the four seasons with molecular weight ranging from 202 to 296 m/z. In all samples, sesquiterpene hydrocarbons were predominating (51.28-90.89%). The antimicrobial screening showed that the essential oils were active on Bacillus Subtilis ATCC 19659 and Staphylococcus aureus ATCC 6538P using the disc diffusion method. The in vitro anticancer activity was investigated against human breast cancer (MCF7), liver cancer (Huh7) and prostate cancer (PC3) cell lines by MTT assay. Results showed that the oil behave as a very potent anticancer agent with the IC50 values of 1.67, 5.78, 6.5 μg ml-1, respectively compared with Staurosporine with IC50 values of 5.75, 8.31 and 4.02 μg ml-1, respectively. It was concluded that the best time for collecting the plant and preparing the oil with higher yield and promising biological activities is during spring and the oil can be used as a candidate for antimicrobial and/or anticancer therapy.