Three children were followed longitudinally for 12 months, between their 11th and 22nd months of life, to document their development of the linguistic expression of the agent concept. The children were observed approximately once a month in play and structured activities designed to elicit nonverbal and linguistic behaviors indicative of the children's awareness of the agent concept. This study describes how the linguistic behaviors (i.e., vocalizations, single-word utterances, and multiword utterances) were paired with emerging nonverbal agentive behaviors over the 12-month period. The children's first vocalizations did not appear to be consistently associated with any nonverbal agentive behaviors. Later vocalizations were consistently paired with directive nonverbal agentive behaviors. With the emergence of the mature cognitive notion of agent, the children produced single-word utterances coding the agent in agent-action-recipient events. And finally, for two of the children, multiword utterances coding two aspects of agent-action-recipient events were produced. The evolution of paired nonverbal agentive behaviors and different utterance types has provided evidence supporting the linguistic expression of an underlying cognitive notion.