To address the issue of early verb learning, this study investigate the effect of sentential contexts on infants' ability to associate words with actions. In a habituation paradigm, 12-, 14- and 18-month-old Japanese infants repeatedly watched computer-animated events in which a fish was engaged in rotating or rocking actions paired with novel words in three contexts: (1) in isolation ("boome" and "seppu"), (2) in a verb frame with a null subject ("[it] is daku/nema-ing"), and (3) in a verb frame with a subject ("boome is daku/nema-ing"). Then, infants alternately watched the same word-action pairs and the switched word-action pairs. Results showed that when the novel words were presented in isolation and in a verb frame with a null subject, the 14- and 18-month-olds, but not 12-month-olds, could associate words with actions. By contrast, when the novel words were presented in a verb frame with a subject, only 18-month-olds, but not 12- and 14-month-olds, could associate words with actions. This suggests that by 14 months, infants might begin to associate words with actions only in simpler sentential contexts.