In New Zealand, 7% of deaths are related to respiratory diseases, and Pacific people are at higher risk. This work investigated the causal effects of early-life nutritional factors on early-adulthood lung function among Pacific Islands Families Study cohort members, who consist of the 1398 individuals born from Pacific Island families in Middlemore Hospital between March and December 2000.A total of 466 people from the cohort participated in the respiratory study. The primary outcome was the forced expiratory volume in 1 s (FEV1) z-score at age 18 years. FEV1 and healthy lung function (HLF), defined as the z-score being larger than −1.64, were secondary outcomes. Nutrition and other information were previously collected in 4 measurement waves at ages 4, 6, 9, and 14 years. Food portions consumed daily were totaled within each of the 12 food categories at each measurement wave. Exploratory and multi-group confirmatory factor analyses identified 4 eating patterns represented by nutritional factor scores (NFS), identified as “Occasional”, “Seafood”, “Fruit and vegetables”, and “Meat”. The NFS were scaled to portions per day. Confounders were identified using a causal-directed acyclical graph. Semi-parametric linear and relative risk regression models were fitted to estimate the causal effects of NFS on respiratory outcomes, using estimated weights compensating for attrition-induced selection bias. The population-attributable fractions of HLF for each NFS were estimated for each measurement wave. HLF cohort prevalence was estimated at 90% (95% confidence interval [CI] [0.86, 1.00]), lower than the expected 95%. Only the “Fruit and vegetables” eating pattern at 9 years was found to have a statistically significant causal effect on the FEV1 z-score in early adulthood (change in FEV1 z-score: +0.25, 95%CI [0.00, 0.43]). The proportion of HLF attributable to the “Fruit and vegetables” eating pattern at 9 years was estimated at 11% (95%CI [0.00, 0.19]). Results suggest a positive impact of consuming more fruit and vegetables during childhood on respiratory health later in life. There is a need to support healthier food environments for Pacific children and provide access to healthier food choices.