Content based language instruction can assist English as a second language (ESL) students to achieve better learning and teaching outcomes, however, it is primarily used to understand content, and may not help to develop critical analysis skills. Here we describe a pilot study that used a "Socratic" small-group discussion in addition to content based instruction, to enhance critical thinking skills in ESL Biomedical Science students. Students were provided a detailed protocol for the analysis of a research journal manuscript and participated in a Socratic discussion. Students wrote evaluative pieces to summarize the manuscript's topics, both before and after the small-group discussion. Overall, a third of all students displayed an improved critical thinking score based on Bloom's taxonomy. However, only 20% of ESL students improved their critical thinking score, while 42% of non-ESL students improved. Despite this, students agreed that the Socratic discussion improved their understanding of science and enhanced their ability to review scientific literature. Importantly, ESL students believed that the discussion made them feel positive about their ability to read scientific literature. Thus, specific tools for enhancing critical thinking in the ESL student group should further be developed, with investigation of the retention of these skills warranted.