To evaluate predictors of implant length for men undergoing primary IPP placement. A multicenter, retrospective cohort study was performed for men undergoing primary IPP placement at 16 high-volume surgical centers. Patient demographics, comorbidities, operative approach, and implanted cylinder and rear tip extender length were recorded. Associations between potential preoperative and intraoperative predictors of total device length were tested using non-parametric correlation and Kruskal-Wallis tests, followed by multiple regression. Of 3,951 men undergoing primary IPP placement from July 2016 – July 2021, the median implant length was 20 cm (IQR: 19 – 22). Shorter implant length was associated with increasing age in years (β = -0.01, p=0.009), Asian ethnicity (β = -2.34, p=0.008), history of radical prostatectomy (β = -0.35, p=0.001), and use of an infrapubic surgical approach (β = -1.02, p<0.001). Black or African American ethnicity was associated with the implantation of longer devices (β = 0.35, p<0.001). No significant associations were recorded with BMI, history of intracavernosal injections, diabetes mellitus, tobacco use, radiation therapy, Peyronie’s disease, priapism, or cavernosal dilation technique. The length of an implanted penile prosthesis was found to be associated with preoperative and intraoperative factors including history of radical prostatectomy and operative approach. The knowledge of these associations may assist in the preoperative counseling of patients receiving IPP and help create accurate postoperative expectations.