The present study was conducted in 2021 to investigate the effect of Farmer Field School on onion productivity in District Swat, Khyber Pakhtunkhwa. The study was carried out in six purposively selected villages of swat namely; Baidara, Kuza Durshkhela, Sinpora, Shamak, Janu Langar and Chalyar. For primary data collection census technique was used. All the twenty five farmers were chosen based on 100 percent of the population from each FFS, resulting in total of 150 respondents from six villages in six union councils. Data were collected by using well-defined and pretested interview schedule. It was found that 34.84% of the respondents were in the age group of 36-45 years. In case of education majority (92%) of the sample respondents were literate and only 8% were illiterate. About 42.21% of the respondents have farming experience of 11-15 years. It is reported that 36.18% of the respondents have land size from 7-9 acres. The total cost on onion production before at the average was Rs. 44010.34 and after FFS was Rs. 34586.99. This does means that the total cost on onion production was reduced by Rs. 9456.51 after FFS. Total yield of onion production before at the average was 8424.66 kg/acre and after FFS was 14210.34 kg/acre. Hence, Total yield of onion crop was increased by 5785.68 kg/acre. The income of onion grower was increased by Rs. 94677.37 per acre from Rs. 271280.8 to Rs. 365958.17 per acre. It was noted that yield and income of the respondents were increased after FFS. It is recommended that more FFSs should be established in other parts of the province to increase agricultural productivity to meet the food needs of the growing population of province.