Early childhood educators (ECEs) play a vital role in encouraging healthy physical activity (PA) in childcare. As such, measuring ECEs' self-efficacy to facilitate such programming is important. The "ECE Confidence in Outdoor Movement, PA, and Sedentary and Screen Behaviors" (ECE-COMPASS) questionnaire (30 items) was developed via expert consensus. A test-retest design was used to assess the reliability and validity of the questionnaire with 165 Canadian ECEs via an online survey administered twice, one week apart. Reliability was assessed using Cronbach's alpha and test-retest statistics, and exploratory factor analysis (EFA) was employed to determine factorial validity. Internal consistency and factorial validity of a revised version of the tool (31 items) was also tested with 120 additional ECEs. The ECE-COMPASS questionnaire showed high internal consistency (Cronbach's alpha > 0.90 across subscales) and modest temporal stability (test-retest statistics > 0.62). A two-factor solution was identified by the EFA for both versions of the tool, with the two-factor solution explaining 10% more variability within the revised version, compared with the original tool. The revised ECE-COMPASS questionnaire was found to be valid and reliable and is recommended for use to measure ECEs' self-efficacy to promote PA and outdoor play and minimize sedentary behaviors in childcare.