Background: We aimed to evaluate the impact of Primary Health Care (PHC) consolidation on child mortality in Latin America over the last two decades, and to forecast the potential PHC mitigation effects during the current economic crises.Methods: This multi-country study integrated retrospective impact evaluations in Brazil, Colombia, Ecuador, and Mexico (BCEM) from 2000-19 with forecasting models up to 2030. We estimated the impact of PHC on under-five mortality rates (U5MR) for different age groups and causes, adjusting for all relevant demographic, socioeconomic and healthcare factors, using fixed-effects multivariable negative binomial models in 5,647 municipalities with adequate quality of vital statistics. We also performed several sensitivity and triangulation analyses. Thereafter, we integrated previous longitudinal datasets with validated dynamic microsimulation models, projecting U5MR trends up to 2030 according to alternative policy scenarios.Findings: Consolidated PHC coverages were associated with significant reductions of post-neonatal (RR:0·72;95%CI:0·71-0·74), toddler (RR:0·75;95%CI:0·73-0·76), and U5MR (RR:0·81; 95%CI:0·80-0·82), and were related to lower U5MR from nutritional deficiencies (RR:0·55;95%CI:0·52-0·58), anemia (RR:0·64;95%CI:0·57-0·72), vaccine-preventable and sensitive conditions (RR:0·70;95%CI:0·68-0·72), and infectious gastroenteritis (RR:0·78;95%CI:0·73-0·84). Considering a scenario of moderate economic crisis, a mitigation strategy that will increase the PHC coverage to protect the new poor could reduce U5MR up to 23% (RR:0·77;95%CI:0·72-0·84) and avoid 142,285 (95%CI:120,22-164,38) child deaths by 2030 in BCEM.Interpretation: The consolidation of Primary Health Care over the last two decades has substantially contributed to improving child survival, and its expansion should be considered an effective strategy to mitigate the health impact of the current economic crisis.Funding: This study received funding from the Medical Research Council (MRC) UKRI, Grant_Number: MC_PC_MR/T023678/1. DR acknowledges support from the grant CEX2018-000806-S funded by MCIN/AEI/ 10.13039/501100011033, and support from the Generalitat de Catalunya through the CERCA Program.Declaration of Interest: We declare no competing or conflict of interest.