Background: Failure to thrive describes an infant or child who does not gain weight at the expected rate. The current study's objective was to evaluate mothers' expertise and practices regarding care of their infants suffering from failure to thrive. Research design: A descriptive research design was used. subjects: One hundred fifty mothers and their infants from pediatric outpatient endocrine  clinic of Tanta University Hospital and outpatient follow up clinic of Urban medical center of Sidi Salem, Kafr El Sheikh were included. Three Tools were used to collect the required data: Structured interview schedule to obtain socio-demographic characteristics of studied  mothers and their infants, observational checklist to assess mothers^, feeding practice related to care of their infants with failure to thrive and nutritional assessment sheet to assess infant^, growth. The results revealed that, most of mothers who had low and moderate level of knowledge had unsatisfactory practices. Between mothers^, knowledge and practice there is no statistically significant difference. The relationship between mothers' knowledge and their demographic data was statistically significant. Conclusion: there were statistically significant difference between total mothers^, knowledge and practice scores of mothers about failure to thrive and feeding pattern, there were significant relation between mothers^, knowledge and their demographic data. Recommendations: the current study recommended that, in service educational program about failure to thrive and feeding patterns should be conducted at endocrine clinic to mothers of infant with failure to thrive and nurses. Mothers and nurses should have access to a manual logbook about how to care for infants who are failing to thrive in order to improve their practises in endocrine clinic as areference and further study should be conducted about failure to thrive