Parental investment is a unique balance between optimizing reproductive success and survival, yet how individuals vary their effort with respect to age and the contributions of their partner remains poorly studied. Here, we examine the provisioning of nestlings by Wood Thrushes (Hylocichla mustelina) at 38 nests in southern Indiana during the breeding season of 2013 to address the influence of adult age and sex on reproductive investment. We used video cameras to quantify an adjusted provisioning rate (provisioning rate = adult visits/hr/nestling × mean prey size × mean number of prey/visit) by individuals in both age-assortative (same age) and disassortative (different age) pairs (n = 33 pairs), hereafter referred to as pair type. Disassortative pairs delivered less prey than expected given nestling age, and sexes differed in their respective provisioning effort. In contrast, age-assortative pairs consistently provisioned more, and provisioning effort was comparable between the sexes regardless of parental age. These findings are contrary to studies where older breeders had a greater foraging efficiency and provided young with more prey. Our results indicate that adult age is not an accurate predictor of provisioning in Wood Thrushes and highlight the previously overlooked importance of age-assortative mating on parental investment in this system.