It is well known that a major impediment to the successful mastery of a target foreign language (FL) is a lack of exposure outside the classroom. The present one-year longitudinal study set out to examine (1) the amounts and kinds of exposure to English outside class experienced by young learners in an EFL context, (2) the relationships between their exposure and socioeconomic status (both parents’ education levels and household incomes), and (3) the association between exposure and vocabulary gains. Ninety Grade-5 EFL children in Hong Kong completed a pre- and post-vocabulary test with a gap of 1 year. Individual interviews were conducted with each child’s parent(s)/guardian(s) (and the children themselves) to collate data about their backgrounds and the child’s exposure to English. The findings revealed that all participants received out-of-class English input through doing homework, and more than two-thirds of them attended tutorial classes and engaged with general informal exposure to English (GIE) such as watching videos and reading books. (Marginally) positive correlations were found between GIE, household income, and parents’ levels of education. GIE was also found to be related to total vocabulary gains over the one-year period, especially at the 2,000-word level.