Postharvest sprouting poses a major challenge for the potato industry, reducing seed quality and causing economic losses. Seed quality is an important factor influencing the yield. SmartBlock^® and 1,4-DMN are new chemicals used to control sprouting. This study evaluated the effects of these suppressants on the nitrogen use efficiency (NUE) and growth of treated seed potatoes. ‘Panamera’ and ‘Mondial’ were treated with 0.100 mL kg⁻¹ × 4 dosages of SmartBlock^® and 1,4-DMN and stored in the dark. Treated seeds were planted in the field one week after the last application. The trial was arranged in a split–split plot design with 50 and 100% nitrogen as the main block, suppressants as the subplot, and cultivar assigned to plots, and replicated three times, including the control. Emergence percentage and index, leaf area, chlorophyll, stem number, tuber form index, and tuber yield were recorded, and NUE was calculated as yield (kg)/kg N input. 1,4-DMN significantly reduced the emergence percentage and index in ‘Panamera’ under 100% nitrogen, whereas SmartBlock^® increased the emergence index only at 50% nitrogen. SmartBlock^® and 1,4-DMN significantly increased stem number in ‘Panamera’, while 100% nitrogen increased chlorophyll. At 50% nitrogen, SmartBlock^® produced oval-shaped tubers, whereas the control produced short-oval tubers. NUE and yield increased in all treatments except SmartBlock^® at 50% N. Effects were limited in Mondial. Overall, 1,4-DMN increased NUE and yield under both full and reduced nitrogen application, suggesting its suitability for use by resource-constrained and commercial producers.