Background: Men with localized prostate cancer must select from multiple treatment options, without one clear best choice. Consequently, personal factors, such as knowing other prostate cancer patients who have undergone treatment, may influence patient decision-making. However, associations between knowledge about others’ experiences and treatment decision-making among localized prostate cancer patients has not been well characterized. We used data from a population-based cohort of localized prostate cancer patients to examine whether patient-reported knowledge of others’ experiences is associated with treatment choice. Methods: The North Carolina Prostate Cancer Comparative Effectiveness & Survivorship Study (NC ProCESS) is a population-based cohort of localized prostate cancer patients enrolled from 2011-2013 throughout the state of North Carolina in collaboration with the North Carolina Central Cancer Registry. All patients were enrolled prior to treatment and followed prospectively. Patient decision-making factors including knowledge of others’ experiences with prostate cancer treatment options were collected through patient report. Patient treatment choice was determined through medical record abstraction and cancer registry data. Results: Among 1,202 patients, 17% reported knowing someone who pursued active surveillance (AS) while 28%, 46%, and 59% reported knowing someone who received brachytherapy, external beam radiation (EBRT), or radical prostatectomy (RP), respectively; 26% underwent AS, 9% brachytherapy, 21% EBRT, and 39% RP as their initial treatment. In unadjusted analyses, patients with knowledge of others’ experiences with brachytherapy, EBRT or RP had more than twice the odds of receiving that treatment compared to patients who did not. Knowledge of others’ experience with AS was not associated with choice to undergo AS. Multivariable analysis adjusting for age, race, risk group, and patient-reported goals of care showed knowledge of others’ experiences with brachytherapy (OR 4.60, 95% confidence interval [CI] 2.76 to 7.68), EBRT (OR 2.38, 95% CI 1.69 to 3.34), or RP (OR 4.02, 95% CI 2.84 to 5.70) was significantly associated with odds of receiving that treatment. The odds of receiving a particular treatment option were further increased among patients who reported knowing someone who had a “good” experience with the treatment in question. Conclusions: This is the first population-based study to directly demonstrate the impact of a patient’s knowledge of others’ experiences on treatment choice in prostate cancer. These data provide a new consideration to clinicians in their counseling of patients with newly diagnosed prostate cancer, and also impacts research into the informed decision-making process for this disease.