Content and Language Integrated Learning (CLIL) has a dual focus both on content and language teaching in which students learn through and about language and provides contextualized and meaningful situations. Although studies on the impact of CLIL on learners' vocabulary knowledge and reading comprehension have mostly positive results, related research is highly limited in Turkish context. Thus, this study aims to examine to what extent CLIL students differ from non-CLIL students in terms of their reading comprehension and vocabulary size (i.e. receptive and productive). Data were collected from 124 fifth-grade students by means of the reading parts of the Cambridge Key English Test, the 2,000-word frequency-band of the Vocabulary Levels Test (Schmitt, Schmitt, & Clapham, 2001), and the adapted version of the Vocabulary Knowledge Scale (Paribakht & Wesche, 1997). Results of the study showed that the CLIL students significantly outperformed their non-CLIL counterparts in reading comprehension, receptive and productive vocabulary knowledge.