Hydrogen cyanamide is used in areas with inadequate winter chilling to increase fertility and budbreak uniformity in many fruit tree species. This study examined the effect of hydrogen cyanamide (Dormex) on budbreak ofActinidia deliciosa’Hayward’ in relation to time of application and cane length. Treatment times were 8, 6, 4, and 2 weeks before expected budbreak. For each application time, 6‐, 12‐, or 18‐bud long canes were treated. Treatments were arranged in a complete randomised block design with five plants per treatment time. Canes treated 8 and 6 weeks before expected budbreak reached the advanced open cluster stage 15–35 days earlier than untreated canes. Cyanamide shortened the time‐lapse from bud swelling to cluster opening in all the treatments dates and increased cane fruitfulness by increasing the number of flowers per bud and per fruiting shoot. The earliest application enhanced budbreak but did not significantly increase the percentage of fruitful buds, whereas the percentage of flowering shoots in canes treated 2 weeks before expected budbreak was double than that of untreated canes, regardless the cane length. A significant interaction occured between cane length and treatment date. Untreated canes produced the largest shoots.