The present study was conducted to investigate differences in nurturant fathering, father involvement, and young adult psychosocial functioning among small samples of three nontraditional family forms. A total of 168 young-adult university students from three family forms (27 adoptive, 22 adoptive stepfather, 119 nonadoptive stepfather) completed retrospective measures of nurturant fathering and father involvement and measures of current psychosocial functioning. Results indicated that adoptive fathers were rated as the most nurturant and involved and that nonadoptive stepfathers were rated as the least nurturant and involved. In adoptive families, young adults' ratings of paternal nurturance and involvement were strongly and positively correlated with their reports of current psychosocial functioning. The relationships of family form to reports of fathering appeared to be moderated by the child's age at father entry and the number of years of involvement in the child's life. (Contains 1 note and 3 tables.)