The objective was to determine the relationship between knowledge and care in the event of post-vaccination reactions in mothers with children under 1 year of age, at the IPRESS I-4 Bellavista Nanay, Iquitos 2024. Quantitative, observational, descriptive, cross-sectional and correlational study; The population was made up of 45 mothers. The survey and home visit were used as a technique; Instruments: a questionnaire on knowledge about post vaccination reactions and a questionnaire on care for post-vaccination reactions (validity 89.17% and 89.58%) and (reliability 80.01% and 82.95%).The results obtained were: 64.4% of mothers had low knowledge of post-vaccination reactions (local and systemic), 35.6% medium and 0.0% high; 51.1% of mothers presented inadequate care for post-vaccination reactions and 48.9% adequate. Regarding care for local post-vaccination reactions in mothers, 86.7% do n...