Father involvement has been associated with positive social, emotional, psychological, developmental, and health outcomes in a child. However, tools for measuring father involvement have not kept pace with the expanding understanding of the roles of fathers, and in the area of child health, are blunt. The purpose of this study was to develop and validate a self-report measure of father involvement in preschooler’s health, the Father Involvement in Health–Preschool (FIH-PS). In Phase 1 (item generation), 47 items were developed based on previous qualitative work and vetted through cognitive interviews with 21 fathers of children ages 3–5 years (preschool). In Phase 2 (psychometric validation), 560 fathers of 3- to 5-year-olds (n = 392 resident, n = 168 nonresident) completed the FIH-PS item bank. Participants were predominantly White (64%), had private health insurance (53%), had a mean age of 33 years, and half of them were married. Item response theory was used to determine measurement scoring. The FIH-PS Scale was reduced from a 47-item bank to a total of 20 items supporting a 4-factor scale made up of Acute Illness, General Well-Being, Emotional Health, and Role Modeling. Following exploratory (n = 280) and confirmatory factor (n = 280) analyses, the scale followed a bifactor structure, was internally consistent (Cronbach’s α = .953), and discriminated among fathers with lower involvement. A sum-to-T score crosswalk table was produced to standardize the scores along a normal distribution (M = 50, SD = 10, range = 10.8–71.3). Future research and clinical applications of the FIH-PS are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved)