Objectives: To evaluate whether the extent of seminal vesicle invasion of prostatic adenocarcinoma can stratify the risk of biochemical recurrence after radical prostatectomy. Methods: We carried out radical prostatectomy for 1309 patients with prostatic adenocarcinoma between 2006 and 2019; 135 (10.3%) patients had seminal vesicle invasion. After excluding patients with neo-/adjuvant therapy, we reviewed 105 patients. We analyzed the correlation of the extent of seminal vesicle invasion and biochemical recurrence-free survival after prostatectomy and adjusted by various clinicopathological factors in multivariate analyses. Seminal vesicle invasion was stratified into three groups; the proximal part from the base was defined as level 1, followed by level 2 and the distal part as level 3. Results: Among the 105 patients, 30 (29%), 54 (51%) and 21 patients (20%) had seminal vesicle invasion at levels 1, 2 and 3, respectively. Median times to biochemical recurrence were 110, 67 and 12 months in patients with levels 1, 2 and 3, respectively (P = 0.002). The extent of seminal vesicle invasion was the independent risk factor for biochemical recurrence in univariate (level 3 vs 1, P = 0.001; level 3 vs 2, P = 0.015) and multivariate analyses (level 3 vs 1, P = 0.025; level 3 vs 2, P = 0.030). Conclusions: The extent of seminal vesicle invasion might be a significant predictor of biochemical recurrence in prostate cancer patients undergoing radical prostatectomy.