The aim of our study was to examine the relationship between access to the mental lexicon, working memory and knowledge of English (L2) vocabulary. Analyses were undertaken amongst monolingual speakers of Polish (26 with dyslexia, 24 without) who studied English as a second language as part of their compulsory educational programme at school. We assumed that students with dyslexia would manifest deficits in access to the mental lexicon and verbal working memory, and would have a limited L2 vocabulary. We also assumed that better access to the mental lexicon facilitates knowledge of English (L2) vocabulary, and that this relationship is present in both the criterion and the control group. All of the students participated in both parts of the assessment, the group part (i.e., questionnaire, IQ test, two vocabulary tasks) and the individual part (i.e., psychological measures: verbal working memory, RAN, verbal fluency, and single word reading in L1 task). We found that students with dyslexia exhibited deficits in the speed of access to data from the mental lexicon. The predictive function of memory for vocabulary was more conspicuous in the control group; in the criterion group, the result might constitute a risk factor for L2 vocabulary acquisition in dyslexia, which may manifest with increased proficiency in word knowledge. Poor vocabulary knowledge renders the L2 learning experience difficult, as it impairs students' reading comprehension, writing and conversational skills.