Identify mechanisms reported in primary health care (PHC) interventions in rural and marginal urban populations from 1997 to 2019.A scoping review was used to identify the literature. The literature search was conducted using the Medline (PubMed and Ovid), Global Health, Embase, Web of Science, Scopus, and Lilacs databases. Inclusion criteria considered literature on primary intervention and observational studies using qualitative, quantitative, or mixed methods. Articles in English, Portuguese, and Spanish published from 1997 to 2019 were included. Rayyan QCRI was used for definitive document selection; sources of information from gray literature or research in progress were excluded.At the individual level, three groups of mechanisms were identified: levels of relationships between interventions and subjects, transformations that can occur in individuals, and reciprocal relationships. At the institutional level, mechanisms were related to temporality, money, power relations, trust relations, the health system, expectations, and administrative conditions.Individual mechanisms are similar in different contexts. Institutional mechanisms are susceptible to variations in context and are expressed in terms of temporality, economic resources, power and trust relations, the health system, expectations, and administrative conditions.