This thesis evaluates the degree of conventionalization of harmful immigration metaphors. Previous research has identified common tropes of metaphors used to discuss immigration and has additionally demonstrated the effects that metaphors have on conceptualization. In order to assess conventionalization, this study compares the use of dehumanizing metaphors in immigration discourse between politically-left and politically-right news outlets. Forty articles were analyzed using an amended version of Pragglejaz Group’s ‘method for identifying metaphorically used words in discourse,’ with twenty articles representing politically-left news outlets and twenty articles representing politically-right news outlets. Further distinctions were made between news outlets categorized as right vs. right-leaning and left vs. left-leaning. The frequency and tropes of metaphors in sources across the political spectrum were then compared using statistical tests. In regards to frequency, right-leaning news outlets were found to have the highest rate of negative metaphor use compared to other political categories. In regards to trope usage, right and right-leaning news outlets were more likely to use the CRIMINAL metaphor trope than their political counterparts, while left and left-leaning news outlets were more likely to use the OBJECT trope. Overall, this study found that the most likely negative immigration metaphor trope to become conventionalized is the NATURAL DISASTER trope.