The experiment was conducted at Agricultural Research Station, Mannuthy in the year 2018 with the rice variety ‘Jyothi’. The experiment was laid out in RBD with three replications. Treatments included recommended and double the recommended doses of 2,4-D, metsulfuron-methyl + chlorimuron-ethyl and penoxsualm and two controls (hand weeded and unweeded). Herbicides were sprayed at 20 days after sowing (DAS). Biochemical parameters were estimated at one week after herbicidal application and at the time of flowering. Biochemical parameters such as soluble protein, total amino acid and nitrate reductase enzyme activity showed a decline in herbicide treatments compared to hand weeded control. Proline content and catalase enzyme activity showed an increase with herbicide application while other physiological parameters like Indole acetic acid (IAA) content, chlorophyll content, stomatal conductance and net photosynthesis showed a decline. Double the recommended dose of herbicides affected these parameters more adversely as compared to the recommended dose of herbicides. Even though double the recommended dose of herbicide exhibited higher weed control efficiency, it reduced the yield of rice plant.