background: neonatal abstinence syndrome (nas) is a complex disorder, observed in infants experiencing symptoms of withdrawal, as a result of in utero exposure to the maternal use of opioids. breastfeeding has been recognized as the optimal source of nutrition for infants. while the advantages associated with breastfeeding are undisputed, the promotion of breastfeeding for infants diagnosed with neonatal abstinence syndrome is inconsistent. there is evidence to suggest that breastfeeding infants who have been exposed to opioids in utero may improve nas outcomes. aim: a systematic review was conducted to assess and critically appraise the existing literature regarding the effect of infant feeding method among infants with neonatal abstinence syndrome (nas) on neonatal outcomes. method: a systematic search of the literature of feeding methods among infants with nas was conducted using the electronic databases pubmed, cinahl, nursing and allied health, pyschinfo, evidence based medicine, web of science, and medline (embase). studies were eligible for inclusion in the review if they fulfilled the following criteria: (1) reported original data on outcomes related to infant feeding and nas, (2) the study method included any type of quantitative design that included an inpatient comparison group of breastfed and formula fed infants with nas, and (3) the articles were published in english in a peer reviewed journal. all articles selected for inclusion were assessed for methodological quality by first and secondary author using the jbi standardized critical appraisal checklist for cohort/case control studies and the jbi standardized critical appraisal checklist for randomized controlled studies. the principal author extracted the data from the full text studies and entered it into a data extraction template developed for the systematic review. the secondary authors independently reviewed and compared the extracted data. the data was synthesized narratively due to the diverse study samples and outcomes that were evaluated. results: the search identified 491 studies, of which 17 provided information related to nas and infant feeding method. eight studies met the inclusion and exclusion criteria after further examination of the full-text studies. the majority of studies found that breastfeeding was associated with a reduced need for pharmacologic treatment and a decrease in the duration of pharmacotherapy when compared to formula-fed or combination-fed infants. breastfeeding, when compared to formula-feeding, was also consistently associated with a shorter hospitalization and a reduced severity of nas, including lower finnegan scores. studies also identified a later time to withdrawal and a delayed onset of nas associated with breastfed infants when compared to formula-fed infants. conclusions and relevance: the studies consistently identified a trend towards improved nas outcomes for infants who were breastfed when compared to formula or combination-fed. these findings provide evidence for breastfeeding as an effective non-pharmacologic treatment for nas. breastfeeding among stabilized mothers on opioid maintenance therapy (omt) should be recommended as a non-pharmacologic approach to improving nas outcomes.