["Child: Care, Health and Development, Volume 52, Issue 2, March 2026. ", "\nABSTRACT\n\nBackground\nResearch globally has highlighted the crucial role of the early‐life home environment in shaping children's long‐term development. We examined changes in the quality of the home environment during infancy and its associations with child cognitive development at age 3, focusing on Thai children from socioeconomically disadvantaged families.\n\n\nMethods\nTwo‐hundred and eighty mother–child dyads from a Thai birth cohort completed home visits in which demographic data were collected and the IT‐HOME interview completed when the child was 1 and 2 years old. The Bayley‐III cognitive scale was administered at 3 years old.\n\n\nResults\nOur regression analysis revealed significant associations between the quality of the home environment at 2 years (B = 0.30, SE = 0.14, p = 0.028, 95% CI: [0.03, 0.56]), but not 1 year (B = 0.11, SE = 0.11, p = 0.279, 95% CI: [−0.09, 0.32]), and cognitive development at 3 years. Furthermore, positive changes in the quality of the home environment from 1 to 2 years were significantly associated with better cognitive development (B = 0.30, SE = 0.14, p = 0.028, 95% CI: [0.03, 0.56]).\n\n\nConclusion\nOur results underscore the importance of both the immediate quality of the home environment and its improvements over time. We suggest that future studies expand to include more diverse demographic backgrounds within Thai culture and across different cultures, collect data over a longer period to capture associations at older ages, and develop targeted interventions to further understand and improve child cognitive development through an optimal home environment.\n\n"]