This systematic review investigated how successful children/adolescents with poor literacy skills are compared to their peers with typical literacy skills in learning a foreign language. Moreover, we explored whether specific characteristics related to participants, foreign language instruction and assessment moderated scores on foreign language tests in this population. Overall, 16 studies with a total of 968 participants (poor reader/spellers: *n* = 404; control participants: *n* = 564) met eligibility criteria. Only studies focusing on English as a foreign language were available. Available data allowed for meta-analyses on 10 different measures of foreign language attainment. In addition to standard mean differences (*SMD*s), we computed natural logarithms of the ratio of coefficients of variation (*CVR*s) to capture individual variability between participants groups. Significant between-study heterogeneity, which could not be explained by moderator analyses, limited the interpretation of results. Although children/adolescents with poor literacy skills on average showed lower scores on foreign language spoken word production, phonological awareness, letter knowledge, and reading comprehension measures, their performance varied significantly more than that of control participants. Thus, it remains unclear to what extent group differences between the foreign language scores of children/adolescents with poor and typical literacy skills are representative of individual poor readers/spellers. Taken together, our results indicate that foreign language skills in children/adolescents with poor literacy skills are highly variable. We discuss limitations of past research that can guide future steps towards a better understanding of individual differences in foreign language attainment of children/adolescents with poor literacy skills. *Keywords: poor literacy, dyslexia, foreign language, bilingualism, meta-analysis* Published article available at http://link.springer.com/article/10.1007/s10648-020-09566-6