Background: Population-based studies assessing various active surveillance (AS) protocols for prostate cancer, to date, have inferred AS participation by the lack of definitive treatment and use of post-diagnostic testing. This is problematic as evidence suggests that most men do not adhere to AS protocols. We sought to develop a novel method of identifying men on AS or watchful waiting (WW) independent of post-diagnostic testing and aimed to identify possible predictors of follow-up intensity in men on AS/WW. Methods: A predictive model was developed using SEER watchful waiting data to identify men ≥66 years on AS between 2010–2015, irrespective of post-diagnostic testing, and applied to SEER-Medicare database. AS intensity among different variables including age, prostate-specific antigen (PSA) level, number of total and positive biopsy cores, Charlson comorbidity index, race (Black vs. non-Black), US census region, and county poverty, income, and education levels were compared using multivariable regression analyses for PSA testing, surveillance biopsy, and magnetic resonance imaging (MRI). Results: A total of 2238 men were identified as being on AS. Of which, 81%, 33%, and 10% had a PSA test, surveillance biopsy, and MRI scan within 1–2 years, respectively. On multivariable analyses, Black men were less likely to have a PSA test (adjusted rate ratio [ARR] 0.60, 95% CI: 0.53–0.69), MRI scan (ARR 0.40, 95% CI: 0.24–0.68), and surveillance biopsy (ARR 0.71, 95% CI: 0.55–0.92) than non-Black men. Men within the highest income quintile were more likely to undergo PSA test (ARR 1.16, 95% CI: 1.05–1.27) and MRI scan (ARR 1.60, 95% CI 1.15–2.27) compared to men with the lowest income. Conclusions: Black men and men with lower incomes on AS underwent less rigorous monitoring. Further study is needed to understand and ameliorate differences in AS rigor stemming from sociodemographic differences.