Although it is well accepted that parents greatly impact infant development, it is less clear which factors impact change in quantity and quality of parenting across infancy. This longitudinal study (N = 120 families) investigated how infant temperament and marital adjustment related to trajectories of mother and father involvement and sensitivity across infancy using multilevel models. Parental involvement (caregiving and play), infant temperament (surgency, negative affectivity, regulation), and marital adjustment were assessed from questionnaires when the infant was 3, 5, 7, 12, 14, and 20 months of age; parental sensitivity was coded from two episodes of the Still-Face Paradigm in early infancy (3, 5, and 7 months). On average, mothers showed higher levels of caregiving, play, and sensitivity than fathers. Mother caregiving, play, and sensitivity increased over time. Father caregiving and play also increased over time, whereas sensitivity did not change with age. Happier marriages were related to increased play for both mothers and fathers. Infant surgency was also significantly related to caregiving, play, and sensitivity trajectories for mothers but not fathers. Findings are discussed in relation to parenting roles and family dynamics.