This work explores underutilized peels and seeds lemon (Citrus limon L) extracts for their phenolic contents and in vitro antimicrobial activities. In this study, phenolics and flavonoids contents were found to be more present in the peel extract (30.10 ±2.98 mg of GAE/g) and (19.78±0.10 mg of QE/g) respectively compared to the seeds extract (14.51 ±1.22 mg of GAE/g) and (0.12±0.009 mg of QE/g) respectively. Phytochemical study showed the presence of quercetin in both extracts as gallic acid was identified only in the peels extract. The antimicrobial activity of peels and seeds extracts was tested against six pathogen bacteria and one fungal strains using disk diffusion method. Results of this research indicated that peel extract presented an important activity on all tested strains, that grampositive bacteria were more susceptible than gram-negative bacteria. The most susceptible gram-positive bacteria was Staphylococcus epidermedis with 31mm diameter of inhibition zone. Exceptionally Staphylococcus epidermedis and Pseudomonas aeroginosa that showed zone of inhibition against seeds extract with diameter of 9mm, 11mm respectively. So, the peel extract had an inhibitory effect more than seeds extract. It could be concluded that peels extract of this plant can be explored as an economically viable source of naturel antimicrobials which can be used as an alternative for antibiotics.