The study was conducted to determine farmers’ knowledge, attitude, and practice regarding onion cultivation and to explore the contribution of their selected characteristics to their knowledge, attitude, and practice regarding onion cultivation. Data were collected from 240 onion farmers of Modhukhali and Sadar Upazillas under Faridpur district with the help of pretested interview schedule during the period from 01 March to 10 April 2024. The majority (59.2%) of the onion farmers had medium knowledge, compared to 26.3% and 14.6% of them had high and poor knowledge on onion cultivation. The majority (73.8%) of the onion farmers had a low favorable, compared to 19.6% and 4.6% had medium and high favorable attitude towards onion cultivation. Above half (51.25%) of the farmers had high practice, compared to 28.75% and 20.0% of them had moderate and low practice of modern onion cultivation. Each of knowledge, attitude and practice regarding onion cultivation had a significant relationship with others. Onion cultivation practice, group contact, BCR, individual contact, time spent in onion farm, commercialization of onion, and attitude towards onion cultivation of the farmers had a significant contribution to their onion cultivation knowledge. Group contact, onion cultivation practice, and onion cultivation knowledge of the farmers had significant positive contribution to their attitude towards onion cultivation. Knowledge on onion cultivation, commercialization of onion, onion farming experience, and attitude towards onion cultivation of the farmers had a significant positive contribution to their onion cultivation practices. Proper onion cultivation knowledge can form favorable attitude towards onion cultivation which can increase more modern onion cultivation practices.