Background Childhood obesity has reached epidemic proportions. There is increasing attention to the topic of prevention and continued debate as to whether breastfeeding (BF) is protective against childhood obesity. Previous systematic reviews on this topic were done in 2005 showing that BF was protective against childhood obesity but, because of confounding variables, the evidence was weak. Objective To explore the current evidence of the effect of BF on childhood obesity and provide recommendations for the nurse practitioner (NP) as a primary care provider. Methods A systematic review of the literature from 1/2005 to 3/2012 was done to assess the evidence on the relationship between BF and childhood obesity. Results The majority of studies identified in this article showed a relationship between BF and obesity prevention, but because of confounding maternal, child, cultural, genetic, and environmental variables, the relationship remains unclear. Conclusions While it is possible that there are protective benefits of BF on childhood obesity, it is difficult to prove because of confounding variables. However, because of other benefits for the mother and child, BF should be encouraged. Whether obesity in childhood can be prevented by BF remains unclear. Further research controlling for confounding variables is needed to provide concrete evidence.