The current study investigates the extent to which receptive vocabulary size test scores can predict second language (L2) speaking ability. Forty-six international students with an advanced level of L2 proficiency completed a receptive vocabulary task (Yes/No test; Meara & Miralpeix, 2017) and a spontaneous speaking task (oral picture narrative). Elicited speech samples were submitted to expert rating based on speakers' vocabulary features as well as lexical sophistication measures. Results indicate that vocabulary size was significantly associated with vocabulary rating. However, learners with large vocabulary sizes did not necessarily produce lexically sophisticated L2 words during speech. A closer examination of the data reveals complexities regarding the relationship between vocabulary knowledge and speaking. Based on these findings, we explore implications for L2 vocabulary assessment in classroom teaching contexts and provide important suggestions for future research on the vocabulary-and-speaking link.