Children and adults are guided by verb-specific syntactic likelihoods, or verb bias, in language comprehension and production. Recent reports showed that verb bias can be altered by new linguistic experience. We investigated the mechanisms underlying this verb bias learning or adaptation. Specifically, we asked whether verb bias learning, like abstract syntactic priming, is driven by error-based implicit learning. We report three experiments in which we altered the biases of familiar dative verbs in children’s and adults’ sentence production, via training trials that induced participants to produce each verb consistently in either double-object or prepositional-object dative structures. Participants’ syntactic choices in later test trials reflected the expected adaptation of verb bias to the training experience. In addition, the magnitude of the training effect varied with the likelihood of each sentence structure and with pre-existing verb bias: Unexpected verb-structure combinations resulted in larger training effects, suggesting the operation of error-based implicit learning.