Ergonomics is important to study the relation between man and machine as this science involves the application of objective data concerning the user group expected to use the equipment. Considering the importance to ergonomic study, existing walk-behind type battery-assisted 350W DC motor operated power weeder was selected for assessment on selected ergonomic parameters such as heart rate, anthropometry, strength, safety, body part discomfort score, overall discomfort score, lumbar motion parameter, and rapid entire body assessment including mechanical aspects. Based on the ergonomic study on the selected weeder, the feedback was observed related to handle, safety and power transmission unit during operation. The selected existing unit was modified as per the ergonomic observations and an ergo-compliant 350W DC motor operated power unit was developed by modifying handle and safety cover. A U-type handle having telescopic arrangement was designed in this ergocompliant weeder to accommodate 90% user group of male and female farm workers by adopting geometric technique. In addition to handle, a safety cover was provided on moving parts and power transmission unit. The weight of ergo-compliant unit was 42kg. This ergo-compliant power unit reduced 8.33 and 5.26% heart rate of worker in operation of three tine shovel type and sweep type cultivators, respectively as compared to existing power unit. The work load was shifted from “heavy category” to “medium category”. There were no significant changes in twisting velocity, sagittal flexion and lateral velocity of subjects during the operation of both existing and ergo-compliant power units. The effective field capacity of three tine shovel type cultivator was 0.0522 ha/h while capacity of sweep type cultivator was 0.0444 ha/h with ergo-compliant power unit at about 2 km/h. The weeding efficiency was 15.2% higher for sweep type than three-tine shovel type cultivator with ergo-compliant power unit. The ergonomic study clearly showed better performance of ergo-compliant power weeder to existing one.