This study examined family functioning at mealtime, a context relevant to the management of cystic fibrosis (CF). Thirty-three families of children with CF and a control sample of 33 families of children without a chronic illness were assessed. Family functioning was rated during a videotaped dinner using the McMaster Mealtime Interaction Coding System (MICS), and mealtime behavioral problems were assessed using the Behavioral Pediatrics Feeding Assessment Scale (BPFAS). Ratings for families of children with CF were lower than for control families on overall functioning and five of six MICS dimensions (Communication, Interpersonal Involvement, Behavior Control, Affect Management, Roles). In families of children with CF, better family functioning was related to less frequently occurring mealtime behavioral problems (BPFAS); however, family functioning was not related to the child's weight status or the child's caloric intake. Data support that nutritional intervention may be maximized if dietary adherence is promoted in the context of positive parent-child and family interactions.