Recent studies report a striking decline in children’s ability to notice same-different relations around age 3 (Walker et al., 2015). We propose that such a decline results from an object focus related to children’s avid noun-learning. To test this, we examine children’s performance on a classic relational task – the relational match-to-sample task (RMTS). Prior work has shown that 4-year-olds can pass this task (Christie & Gentner, 2014). However, if nominal language induces an object focus, their performance should be disrupted by a noun-labeling pretask. In two experiments, 4-year-olds either labeled objects or actions in a naming pretask. Then they completed the RMTS task. Consistent with the noun-focus explanation, the object-naming group failed the RMTS task, whereas the action-naming group and a control group both succeeded. This suggests that nominal language can lead to an object focus, and that this could explain the temporary decline in children’s relational processing.