The present paper deals with, the antimicrobial efficacy of lemon seed extract against the growth and development of Pseudomonas aeruginosa (P. aeruginosa) was thoroughly investigated. Different concentrations of 5% to 15% and 20%, and then cultured in two separate characteristics of media as liquid and solid for testing the colony formation as well as to determine the minimum inhibitory concentration (MIC) against P. aeruginosa. The obtained results of this study have indicated that the extract of lemon seeds showed not only the statistically significant reduction of of P. aeruginosa colony formation in order of 5% to 15% and 20%, but also pointed out the statistically significant reduction of P. aeruginosa colony formation at 10% and 13%, with agar test and broth test in the ratio of 1:4 (v/v) respectively. Beside that this project also contributes to useful information for improving medicinal from solution extracts of lemon seed usage against the growth and development of P. aeruginosa. In summary, the lemon seed extract could effectively inhibit the growth of Pseudomonas aeruginosa at the selectively applied concentrations.