ABSTRACT Childhood obesity remains highly prevalent and originates early in life. Efficacious early life interventions to prevent childhood obesity are lacking, particularly among populations most burdened by childhood obesity. Food insecurity - defined as lack of enough food for an active, healthy life – may play key upstream roles in etiologies of obesity through establishment of unhealthy dietary patterns and stress-related metabolic perturbations. Household food insecurity during the first 24 months of life is a risk factor for later childhood obesity. Professional organizations recommend integration of household food insecurity screening into routine pediatric primary care. Yet, a critical gap exists in identification of efficacious clinical interventions to reduce food insecurity. Another gap exists in understanding relationships between food insecurity and etiologies of obesity. Food FARMacia is a clinically based mobile food pantry intervention developed to address the high prevalence of food insecurity among pediatric patients. No randomized trials of a clinically-based mobile food pantry intervention in pediatric primary care exist. To understand the role of food insecurity in etiologies of childhood obesity, efficacious interventions to reduce food insecurity are needed. To test efficacy of the Food FARMacia intervention in a randomized clinical trial (RCT), feasibility of RCT procedures must first be established. The overall goal of this study is to perform a Phase IIb pilot and feasibility RCT of the Food FARMacia clinically based mobile food pantry intervention to promote healthy weight during infancy compared to an attention control over 6 months. We will recruit 70 families (randomized n = 35 infant-parent dyads per arm) with an infant age 6 to <18 months and food insecurity identified on routine electronic health record screening at pediatric primary care visits in our multi-site urban academic health care system. We will examine feasibility and acceptability of the RCT procedures and intervention components using quantitative and qualitative research methods. We will estimate the effects of the intervention on infant weight characteristics over time to inform a full-scale trial. We will explore potential mediators of intervention effects, including household food insecurity. Our multidisciplinary team has expertise in childhood obesity, nutrition, community-engaged, and population health research; clinical trials; qualitative research; and biostatistics. Results will immediately inform a full-scale Phase III RCT to test the efficacy of the Food FARMacia intervention on preventing childhood obesity. Results of a full-scale trial will also provide new information about relationships of household food insecurity during infancy and etiologies of obesity. If successful, this research will accelerate identification of scalable, efficacious clinical interventions to transform clinical care for reduction of food insecurity and promotion...