The alleopathy of rice and weed at the germination stage was evaluated in agar medium. The main objective was to identify the phenolic compounds released in rice and the environment during germination of rice and weeds. The results showed that the germination rate of lettuce significantly decreased when it was germinated together with either dehulled rice or hull. Rice, dehulled rice and hull strongly affected the survival rate of and growth radish, especially root length. The total phenolic and flavonoid contents in the agar media dramatically changed when weeds were germinated with rice. In the medium of dehulled rice and lettuce treatment, the phenolic content significantly increased while flavonoid content decreased, compared to total of the two controls. Gallic acid increased in leaf of dehulled rice germinated with lettuce and radish, which changed from 42.69 mg/g dry weight (control) to 63.35 and 44.76 mg/g dry weight, respectively. Catechol (22.28 mg/g dry weight) was solely produced when rice germinated with radish. High amount of benzoic acid was generated in leaves of rice germinated with lettuce and radish, which constitute 1405.39 and 585.62 mg/g dry weight, respectively. The findings demonstrate that germination of weeds is impacted by the presence of rice, dehulled rice and hull. Catechol and benzoic acid may have the role of an alleochemical in rice.