Vocabulary knowledge is crucial for incidental vocabulary learning through viewing captioned television. This study aimed to evaluate the spoken test format of vocabulary knowledge and its impact on incidental vocabulary learning from captioned television. The research measured the breadth and depth of spoken vocabulary knowledge in 87 minority students learning English as a foreign language in Australia. The vocabulary size test was adopted to assess the breadth of their knowledge. The depth of vocabulary knowledge was through an evaluation of collocational and semantic relationships. The findings revealed that (1) captioned videos facilitate incidental vocabulary learning; (2) there is a strong positive correlation between scores on the breadth and depth of vocabulary knowledge and incidental vocabulary learning from viewing captioned television; and (3) scores on the depth of vocabulary knowledge uniquely contribute to predicting incidental vocabulary learning at the form and meaning recognition level, complementing the predictions made by scores on the breadth of vocabulary knowledge. These results underscore the importance of enhancing the depth of vocabulary knowledge to improve language minority students' incidental vocabulary learning from captioned viewing.