Psychological characteristics pertaining to attachment relationships were measured in mothers of 25 hospitalized failure‐to‐thrive (FTT) infants and mothers of 25 hospitalized, normally growing infants. The groups were matched for race, socioeconomic status, maternal education, and infant's age and sex. Results showed that 96% of mothers of FTT infants were classified as insecure with respect to attachment, as assessed by the Adult Attachment Interview (George, Kaplan, & Main, 1985), compared to 60% of control group mothers. Lack of resolution of mourning over the loss of a loved one was found in 52% of the mothers in the FTT group and in 32% of mothers in the control group. Mothers of FTT infants reported receiving less support from their families and rated their current relationship with their partner as less satisfying. These findings provide empirical support for the widely held clinical notion that FTT in infants is often a relationship disorder between infant and caregiver.