Overweight and obesity (OW/OB) is a pressing health concern among migrant and seasonal farmworker (MSFW) families in the US. The limited number of previously reported research on MSFW families suggests that their unique sociodemographic characteristics and lifestyle predispose them to poor health outcomes including OW/OB. We aimed to synthesize and assess available data on the prevalence and modifiable health determinants of OW/OB in MSFW children and adolescents. Literature search, study selection, data extraction and synthesis, and qualitative assessment of selected studies were performed independently by two authors. Ten cross-sectional studies met the inclusion criteria: articles or dissertations investigating prevalence and association between health determinants and OW/OB in MSFW children and adolescents (<20 years) in the US. The prevalence of OW, OB, and OW/OB ranged from 10%–33%, 15%–37%, and 31%–73%, respectively. Children’s education, household food insecurity, parents’ weight status, parents’ distorted perception of their children’s weight status, and parents’ participation in the federal nutrition assistance program were significantly associated with the children’s and adolescents’ risk of OW/OB. Promotion of culturally relevant public health programs and implementation of a systematic health surveillance plan for MSFWs and their children should be emphasized to combat OW/OB among MSFW children and adolescents.