This study was to assess the spoken vocabulary knowledge and its role in incidental vocabulary learning from captioned television. The participants were a total of 87 minority students learning English as a foreign language in Australia. The breadth of their vocabulary knowledge was measured with a vocabulary size test, while the depth of their vocabulary knowledge was through an assessment of collocational and semantic relationships. The results indicated that (1) captioned videos are helpful for incidental vocabulary learning; (2) scores on the breadth and depth of vocabulary knowledge and incidental vocabulary learning from viewing captioned television are highly and positively correlated; and (3) scores on the depth of vocabulary knowledge can make a unique contribution to the prediction of incidental vocabulary learning at the form and meaning recognition level, in addition to the prediction afforded by scores on the breadth of vocabulary knowledge. The findings highlight a need to improve the depth of vocabulary knowledge for incidental vocabulary learning from captioned viewing.