Despite the widespread consensus among researchers that readers whose first language is Arabic frequently experience major difficulties with word recognition when reading in English, there is little research into the strategic behaviour of first language (L1) Arabic readers when encountering unknown vocabulary in texts written in English. This paper reports a study designed to contribute to our understanding of the types of reading strategy employed by L1 Arabic speakers when reading in English and in particular the types of knowledge sources and contextual clues they rely on when encountering unfamiliar English words. The following research questions were addressed: 1. What are the principle lexical processing strategies employed by Arabic-speaking university students when encountering unfamiliar vocabulary in academic English texts? 2. To what extent does the employment of these lexical processing strategies result in successful identification of the meaning of unfamiliar vocabulary? A pre-test was conducted to provide a measure of the participants’ overall reading proficiency and to ensure the unfamiliarity of the target words. Subsequently, individual reading tasks with concurrent think-aloud sessions were conducted to enable the identification of lexical processing strategies. Two main findings emerged: first, the participants in this study made use of three strategies when dealing with unfamiliar vocabulary; second, these strategies were frequently employed in a noticeably ineffective manner and, in consequence, many of the participants’ attempts at inferencing were conspicuously unsuccessful. The pedagogical implications of these findings are briefly discussed.