With the fast-paced development of technology in today's society, there has been emerging a shift from paper-based reading to digital online reading. While the benefits of exposure to print have been well-established in previous studies, how online reading may impact individuals' literacy development is largely underexplored. The current study investigated if the amount of English reading experience on the Internet could predict EFL students' lexical knowledge and reading comprehension ability. Participants were ninety-seven Vietnamese undergraduate students who were administered a website checklist and a vocabulary size test. Their reading comprehension scores were also collected as measures of their reading abilities. Descriptive statistics, hierarchical linear regression and structural equation modelling were utilized for data analysis. The results indicated that exposure to L2 online text was a significant predictor of the participants' vocabulary size as well as their reading comprehension growth during a course of two years. Pedagogical implications are discussed.