Research has recently highlighted the potential of audiovisual input for incidental vocabulary learning. However, few studies have examined the role that different factors play in incidental vocabulary learning and retention from viewing. This study aims to examine incidental vocabulary learning and retention through viewing a full-length captioned episode of an English TV program and investigate whether this learning and retention are affected by the learnerrelated variable of prior vocabulary knowledge and the item-related variables of frequency of occurrence, contextual clues, lexicalization, word relevance, and visual imagery. A pretest posttest-between-participant design was adopted. Data were collected from 84 Iranian EFL students who were assigned to three pairs of experimental and control groups, receiving one of the following conditions: (a) immediate, (b) 1-week delayed, or (c) 3-month delayed posttests. The experimental groups were exposed to the audiovisual input while the control groups were not. The results demonstrated that incidental vocabulary learning and retention occurred at the level of form recognition and meaning recall. Moreover, it was revealed that learning and retention were affected by frequency of occurrence, contextual clues, lexicalization, visual imagery, and prior vocabulary knowledge, with the effects of the latter three possibly persisting after 3 months.