One of the key transitions in early cognitive development is from participating in face-to-face interactions to engaging in joint attention exchanges. It is known that the ability to jointly attend with another person to an object is essential for the development of abilities such as language in later life. Strikingly, little is known about the function of joint attention in infants in the first year. We developed a novel interactive-live paradigm to assess the neural mechanisms of joint attention in 9-month-old infants. An adult interacted with each infant, and infants' electrical brain activity was measured in two contexts. In the joint attention context, a live adult gazed at the infants' face and then to a computer displayed novel object. In the non-joint attention context the adult gazed only to the novel object. We found that the negative component of the infant event-related potential (ERP), a neural correlate indexing attentional processes, was enhanced in amplitude during the processing of objects when infants were engaged in a joint attention interaction compared to a non-joint attention interaction. These results suggest that infants benefit from joint attention interactions by focusing their limited attentional resources to specific aspects of the surrounding environment.