Prior research has yielded mixed evidence of a relationship between immigrant generational status or acculturation and overweight or obesity among children of immigrants. This study examined socioeconomic status (SES) and economic development of the sending country as additional factors influencing children body mass index (BMI) and as moderating the relationship between parental generational status and BMI. Using data from the kindergarten cohort of the Early Childhood Longitudinal Survey (N=16,664 children) carried out in the USA, the research estimated growth curve models and tested the significance of interaction terms between generational status (i.e., children of the 1.0 generation, who arrived at age 12 or older; children of the 1.5 generation, who arrived between the ages of birth and 11; and children of natives), SES, and the country of origin's gross domestic product per capita. Results indicate that the children of the 1.0 generation from higher-income countries tended to gain more weight than children from lower-income countries. The relationship between family SES and weight gain was positive among the first-generation children and stronger among those from lower-income countries than from higher-income countries. Weight gain was positively associated with generation only among lower SES children from low-income countries. It was negatively associated with generation for higher SES children from low-income countries. The results are consistent with a conceptual model of BMI assimilation that links global nutrition patterns to the levels and socioeconomic variations in BMI among the 1.0-generation and their children, and conceptualizes assimilation as occurring within socioeconomic strata. This approach leads to the expectation that overweight is likely to be positively associated with generation among those from low-income countries (as measured by GDP/capita) with low SES but negatively associated among those from low-income countries with high SES.