During the first year of life, infants possess some of the key social--cognitive abilities required for success in a social world: Infants interpret others' actions in terms of their intentions and can use this understanding prospectively to generate predictions about others' behavior. Exactly how these foundational abilities develop is currently unknown. The goal of this study was to shed light on the developmental mechanisms underlying changes in infants' understanding of intentional actions by documenting relations between infants' intention understanding and other emerging social (joint attention) and motor (means-end and self-locomotion) abilities. Using eye tracking, 8- to 11-month-olds infants' (N = 80) ability to visually predict the goal of an ongoing successful or failed intentional action was examined in relation to their developing means--end, self-locomotion, and joint attention abilities. Results confirmed previous findings showing improvements in infants' ability to interpret and make predictions about others' failed intentional actions. Importantly, results also indicated that parent-report measures of infants' initiating-joint-attention and self-locomotion abilities were associated with the ability to visually predict the outcome of a failed reaching action. These data support the view that infants' social and motor experiences may contribute to changes in their social--cognitive abilities. In particular, joint-attentive social interactions that occur with increasing frequency as infants learn to crawl and walk may shape infants' understanding of others as intentional agents.