Bisphenol A (BPA), an endocrine-disrupting chemical that is used globally in the production of many plastics, is a pervasive environmental contaminant that poses a growing threat to various forms of life. However, data on its impact on invertebrates, particularly echinoderms, remain scarce, and there is no existing research on BPA's toxicity in adult sea urchins. This study investigates the impact of acute BPA exposure (100, 600, and 1500 μg/L for one week) in adult sea urchin Heliocidaris crassispina, focusing on feeding behaviors (including predation and anti-predation behaviors, digestive enzyme activity), reproductive physiology (including gonadal characteristics, sex hormone levels, and expression of reproduction-related genes), and transgenerational effects. Results show that BPA exposure significantly reduces feeding capacity, prolongs response times in behavioral assays, and decreases digestive enzyme activity, indicating impaired energy acquisition. Histological analysis reveals gonadal developmental delays. Biochemical analysis revealed significant alterations in sex hormone levels, with a severe imbalance in their ratios. Gene expression analysis indicates significant changes in reproductive-related genes (up-regulation of reproductive-related gene myp, down-regulation of sex hormone synthesis key gene cyp17), supporting endocrine disruption. Furthermore, BPA exposure leads to developmental delays in offspring, highlighting potential transgenerational risks. Notably, a non-monotonic dose response was observed across several physiological and molecular endpoints, consistent with those seen in other species. These findings provide new insights into BPA toxicity in marine invertebrates, emphasizing its threat to sea urchin populations and coastal ecosystem stability.