Seed dormancy in sunflower is a major constraint affecting timely sowing, uniform crop establishment and continuity in seed supply systems. The present investigation was conducted during 2023 at the Department of Seed Science and Technology, Tamil Nadu Agricultural University, Coimbatore, to assess the dormancy status of sunflower hybrid COH 3 and its parental lines COSF 6A and IR 6 and also to identify the effective dormancy-breaking techniques. Freshly harvested seeds were evaluated at 5-day intervals using sand media until maximum germination was attained naturally. The hybrid COH 3 and female parent COSF 6A had a very weak dormancy, which exhibited the maximum germination (94 and 93 %) at 15 days after harvest (DAH), whereas IR 6 attained maximum germination (94 %) at 30 DAH, exhibiting a moderate dormancy. The seeds were subjected to different dormancy-breaking treatments at 5 DAH, viz., soaking in water, 2 % KNO₃, 50 ppm ethrel and dry heat treatment. After 12 hr of soaking the seeds in ambient laboratory conditions (28 ± 2 ℃ and 65 ± 5 % relative humidity), the seeds were shade-dried and 400 seeds from each treatment were subjected to a germination test in sand medium. Among the dormancy-breaking treatments, the seeds soaked in 50 ppm ethrel for 12 hr recorded the maximum germination percentage in sunflower hybrid COH 3 (93 %) and its parental lines COSF 6A (93 %) and IR 6 (91 %).