Nowadays, people have shown interest in Thai herbs, and in using them as alternative medications. Mirabilis jalapa, or "Ban Yen" in Thai, is cultivated for its ornamental value. In traditional medicine, it has been used in medications and cosmetics. The objective of this study was to develop M. jalapa gel for the treatment of acne. The dried seeds of M. jalapa were extracted with 10 mM sodium phosphate buffer pH 6.3, containing 50 mM NaCl and lyophilized to obtain a crude extract. The protein concentration of crude extract was 16.05mg/ 1 g of dried seeds. In preliminary screening for antibacterial activity, the extract was active against three gram positive bacterias (Bacillus subtilis , Bacillus thuringiensis , Bacillus shaericus). The extract did not cause a skin irritation in humans. The extract showed inhibitory activity against six strains of Propionibacterium acnes, which were representative of microorganisms causing acne at a concentration of 25 mg/ml. The extract, after storage at temperature -20 °C for 6 months, showed activity against P. acnes. The M. jalapa gel preparation was created by incorporating 3% and 5% of crude extract into a gel base. Physical characteristic and protein concentration were used to determine the stability of M. jalapa gel.The M. jalapa gel had good physical properties and showed antibacterial activity against P. acnes. In the stability test of M. jalapa gel, at high storage temperatures the degradation rate of protein in the gel was more than at low storage temperatures. In preliminary clinical studies, the use of 3% and 5% of M. jalapa gel showed a reduction in the case of mild acne, resulting in a slight clinical improvement.