Background: We evaluated the feasibility and efficacy of a decision support intervention designed to help men with low-risk prostate cancer consider active surveillance and standard treatments. The intervention incorporated a decision aid with coaching and question-listing. Our decision aid is the first to include data on long-term survival and side effects from men with prostate cancer undergoing active surveillance, surgery, and radiation. Methods: To develop the intervention, we conducted focus groups using the Nominal Group Technique. We used a survey instrument from the International Patient Decision Aids Standards to measure the stakeholder endorsement of our intervention. To test the intervention, we administered it to newly diagnosed men with low-risk prostate cancer (Gleason sum < = 3+4, stage < = T2N0M0, PSA < = 10 ng/ml) seen at UCSF. Before and after the intervention, we administered a survey with questions from the Decision Quality Instrument for Prostate Cancer. Our primary outcome was change in knowledge as assessed by two multiple-choice items: How many men diagnosed with early stage prostate cancer will eventually die of prostate cancer? How much would waiting 3 months to make a treatment decision affect chances of survival? Correct answers were: “Most will die of something else” and “A little or not at all.”Results: The development phase involved 6 patients, 1 family member, 2 physicians, and 5 other health care providers and four iterations of the intervention until consensus endorsement was reached. In the pilot test, 57 men consented, and 44 received the decision support intervention and completed surveys at both timepoints. Before the intervention, 30/44 (68%) got both questions right, compared to 36/44 (82%) after the intervention. 82% maintained or achieved perfect scores; 16% answered 1 or more incorrectly both before and after the intervention; and 2% answered both items correctly before, but 1 wrong after. Conclusions: This novel decision support intervention was feasible, and appeared to improve knowledge and informed decision-making. Data will guide the development of a larger scale randomized clinical trial to improve decision quality in men with prostate cancer, in the community. Clinical trial information: NCT02451345