Understanding the relationship between social presence and critical thinking is useful for gaining insight into the interaction and discourse of learners online. Further study of how these two presences interact is important because research has shown a wide variety of relationships, both positive and negative, between social presence and critical thinking. The aim of this study is to investigate social presence and critical thinking using discourse analysis in the hope that it will deepen and broaden our understanding of the relationship between these important facets of learner discourse. Using quantitative analysis, an online forum used by students at a national university in Korea (n=219) was analyzed by taking 900 forum posts to determine the levels of social presence and critical thinking in each post. The relationships between social presence and critical thinking were analyzed and the results show that social presence and critical thinking have a negative correlation. This highlights the need for awareness of learner discourse, as an increase in social presence may lead to a decrease in critical thinking and vice versa. The likely cause of this is that learners tend not to change the discourse once the discourse within a particular context has been set.