Dyslexia diagnosis and intervention in the first language (L1) has a long history, whereas the foreign and second language (L2) learning aspects of dyslexia have largely been neglected. Thus, the present study aimed to provide intervention in English as a foreign language through multisensory phonics instruction to Iranian Persian--speaking students with dyslexia in order to examine the effects of the noted instruction on their L1 and L2 performance, checked using similar tests of L1 and L2 reading and phonological awareness. Results revealed that instruction in L2 enhanced students' performance in both languages, supporting the Linguistic Interdependence Hypothesis, and certain features of L1 orthography led to specific problems in L2, casting doubt on the accuracy of the Script Dependence Hypothesis.