Failure to thrive increases a child's risk for developmental problems and warrants intensive intervention. At the same time, infants with failure to thrive and their families can present a complex number of issues that need to be addressed for successful outcome. The traditional approach which draws a distinction between organic and nonorganic failure to thrive does not reflect current work in the area and can be too simplistic to help the therapist develop an effective assessment and intervention strategy. This article examines the literature and presents a multi-systems model to organize the factors that can contribute to failure to thrive. By emphasizing the interactive nature of systems the occupational therapist will be able to identify the range of issues for assessment with multiple opportunities for intervention.