The medium of instruction during primary/secondary education for most of the Sri Lankan student is either Sinhala or Tamil languages, and this turns to English once the student enters the university. This retrospective cross sectional study aims to find if proficiency in English language has an influence on academic performance. The Grade Point Averages (GPAs) and the Average English marks of three batches were collected. Relationship between English knowledge and academic performance was analyzed using Spearman correlation statistics. Correlations of GPAs of non-clinical modules and English marks of all batches were; 2005/2006 (p=0.011), 2006/2007 (p<0.001), 2007/2008 (p<0.001) and GPAs of clinical modules and English marks of all batches were; 2005/2006 (p=0.032), 2006/2007 (p=0.001), 2007/2008 (p=0.010).Results revealed that there is significant positive relationship between GPAs of non-clinical and clinical modules and English marks of all batches, which shows that knowledge of English has an influence on academic performance. Furthermore, knowledge of English has a higher impact on academic performance of non-clinical modules.