Patients who undergo penile prosthesis implantation as treatment for erectile dysfunction commonly complain of penile shortening after implantation. We conducted a study to determine whether knowledge of pre-operative stretched penile length measurement influences patient satisfaction. This prospective study consisted of 149 patients undergoing inflatable penile prosthesis (IPP) implantation from August 2017 to December 2019. Study group participants underwent pre-operative stretched penile length measurement in clinic while the control group did not. Six months post-operatively, patients completed a modified 14-item Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) questionnaire to assess overall satisfaction and penile length satisfaction. A total of 102 patients were eligible for final analysis (49 in study group, 53 in control). Mean scores for overall treatment satisfaction were 3.57 and 3.53 (scale from 0 to 4) in the study versus control group, respectively (p = 0.483). Mean scores for satisfaction with penile length were 4.08 and 4.11 (scale from 1 to 5) in the study vs. control group (p = 0.645). The study suggests that knowledge of pre-operative stretched penile length does not influence post-operative satisfaction after penile prosthesis implantation. Therefore, performing pre-operative measurements in clinic solely for informing the patient may be unnecessary. Current interventions aimed at conserving penile length may be effective at maintaining satisfaction with penile length.Trial Registration- This trial is registered and approved by the IRB committee at our institution, ID: HSC-MS-19-0320.