The study included 1,241 patients undergoing transradial coronary intervention (TRA) from a prospective single-center registry. Incomplete hemostasis (failure to achieve complete hemostasis within 2 hours of continuous compression) occurred in 230 patients, representing 18% of the sample. Initial activated clotting time (ACT) measured after sheath insertion was significantly higher in patients with incomplete hemostasis (146 ± 37 s vs. 136 ± 32 s, p < 0.001). The final ACT measured before sheath removal was also higher in the incomplete hemostasis group (259 ± 85 s vs. 243 ± 72 s, p < 0.001). In multivariate analysis, prolonged initial ACT was associated with a higher risk of incomplete hemostasis (OR 2.41; 95% CI 1.71–3.39; p < 0.001). Prolonged final ACT was an independent risk factor for incomplete hemostasis (OR 2.25; 95% CI 1.52–3.30; p < 0.001). Thus, the study identified higher preprocedural and postprocedural ACT values as independent predictors of incomplete hemostasis after TRA intervention.