Seed priming with ascorbic acid (AsA) has been widely recognized for enhancing early plant development; however, its effectiveness in improving growth, physiology, yield, and nutritional quality of broccoli under field conditions remains limited. This two-year field study evaluated the effects of AsA seed priming on broccoli under Atlantic Canada soil conditions using a randomized complete block design across two field sites. Four treatments were assessed: non-primed control, water-primed (0 mgL-1), and AsA-primed seeds at 1 mgL-1 and 10 mgL-1. AsA priming significantly (p < 0.05) enhanced plant height, canopy length, stem girth, and leaf area, with the greatest improvements observed at 10 mgL-1, resulting in increases of 17.4%, 19.7%, 51.7%, and 69.4%, respectively, compared to the control. Net photosynthesis, stomatal conductance, transpiration, and chlorophyll index, were also significantly improved (p < 0.001). Biochemical analysis showed significant increases (p < 0.05) in chlorophyll a and carotenoid content at 10 mgL-1. Meanwhile phenolics, flavonoids, and most nutrients were not significantly affected (p ≥ 0.05), except for a slight but significant (p < 0.05) reduction in phosphorus concentration at 10 mgL-1. Yield components were significantly (p < 0.05) improved by AsA priming, with 10 mgL-1 increasing primary yield by 38.4% and secondary yield by 80.4%, whereas 1 mgL-1 significantly (p < 0.05) increased the number of secondary heads per plant by 15.3% compared with the control. Overall, AsA seed priming enhanced growth, physiological performance, and yield without compromising nutritional quality, demonstrating its potential as a practical and sustainable approach to improve broccoli production under field conditions.