This purpose of this grounded qualitative study was to understand the father's response to having a child who is overweight. This study was pursued for four reasons that are substantiated in the literature: (1) The literature is rich with studies that explore the influences of the mother/child interaction at it relates to weight. (2) Studies that explore the influences of the parent/child perspective in general, as they relate to weight of the child, tend to focus on maternal influences, while largely ignoring the paternal impact. (3) The limited number of father/child interaction studies suggests that researchers see this relationship as insignificant compared to the maternal influence on a child's weight. (4) Studies that do explore the father's influence tend to look only at paternal genetic factors which contribute to the child's weight. A pool of twelve participant fathers was interviewed who had an overweight child. The participants were drawn from a family medical practice located in upstate New York. Six components emerged as a father's response to having a child who is overweight: (1) Fathers worry. (2) Fathers experience confusion. (3) Fathers minimize their impact. (4) Fathers experience analysis paralysis. (5) Fathers defer responsibility. (6) Fathers engage. A comprehensive theory, the Theory of Interactions Factors That Lead to a Father's Response (TIF), emerged from the data Fathers experience a number of intrinsic inputs as a result of their child's overweight, and they are motivated into engagement regarding their child's weight by a combination of interacting aspects of intrinsic and extrinsic inputs. Implications for social work practice and future research are discussed.