Introduction: Caregivers’ adherence to Child Primary Care (CPC) health recommendations is particularly relevant for the protection of children’s health and promotion of their optimal development. Nevertheless, there are currently no measures to assess it, as the majority of measures are focused on pharmacological treatment adherence instead of adherence to preventive health recommendations. Thus, this paper describes the development and validation of a new instrument to assess caregivers’ adherence to CPC health recommendations regarding children aged between 2 years and 6 years old, which would also be sensitive to the specificities of caregivers in more vulnerable conditions—the CPC-Adherence Scale. Methods: Six hundred sixty-two parents (93.4% women; 6.6% immigrant), living in Portugal and with children aged between 2 years and 6 years, participated in a cross-sectional study using a paper or electronic protocol. The protocol was composed by: (1) the CPC-Adherence Scale; (2) questions regarding experiences in CPC; (3) the European Task Force on Patient Evaluation of General Practice Care (EUROPEP); (4) socio-demographic information. Results: The exploratory and confirmatory factor analyses supported a 2-factor solution: (1) Adherence to a safe psychomotor development (n = 14 items; Cronbach’s Alpha = 0.894); (2) Adherence to nutritional counseling (n = 6 items; Cronbach’s Alpha = 0.608). The CPC-Adherence Scale showed good content and criterion-related validity. It discriminated levels of adherence of caregivers with different levels of knowledge about CPC recommendations, satisfaction with care and different socio-economic and immigrant t status. Discussion: The CPC-Adherence Scale is an innovative and promising measure that may play a relevant role on future research and intervention for the promotion of adherence behaviors in a primary prevention context.