Background: Active surveillance (AS) is offered as a choice to patients with low-risk papillary thyroid microcarcinoma (PTMC). This study aimed to identify patient and physician factors associated with the choice of AS. Methods: We conducted a cross-sectional survey of patients with low-risk PTMC who were enrolled in a prospective study comparing outcomes following AS and surgery. Patients completed a questionnaire to assess their prior knowledge of the disease, considerations in the decision-making process, and reasons for choosing the treatment. We also surveyed 19 physician investigators about their disease management preferences. Variables affecting the patients' choice of AS, including patients' characteristics and their decision-making process, were analyzed in a multivariable analysis. Results: The response rate of the patient survey was 72.8% (857/1177). Among the patients who responded to the survey, 554 patients (128 male; mean age 49.4 ± 11.6 years; response rate 73.4%) with low-risk PTMC chose AS (AS group), whereas 303 patients (55 male; 46.6 ± 10.7 years; 71.8%) chose immediate surgery (iOP group). In the AS group, 424 patients (76.5%) used a decision aid, and 144 (47.5%) used it in the iOP group. The choice of AS was associated with the following variables: patient age >50 years (odds ratio 1.713 [confidence interval, CI 1.090-2.690], p = 0.020), primary tumor size ≤5 mm (odds ratio 1.960 [CI 1.137-3.379], p = 0.015), and consulting an endocrinologist (odds ratio 114.960 [CI 48.756-271.057], p < 0.001), and use of a decision aid (odds ratio 2.469 [CI 1.320-4.616], p = 0.005). The proportion of patients who were aware of AS before their initial consultation for treatment decision was higher in the AS group than in the iOP group (64.6% vs. 56.8%). Family members were reported to have influenced the treatment decisions more in the iOP group (p = 0.025), whereas the AS group was more influenced by information from the media (p = 0.017). Physicians' attitudes regarding AS of low-risk PTMC tended to be more favorable among endocrinologists than surgeons and all became more favorable as the study progressed. Conclusions: Emerging evidence suggests that physicians' attitudes and communication tools influence the treatment decision of low-risk PTMC patients. Support is needed for patient-centered decision making. (Clinical trial No: NCT02938702).