This study applies the semi-automated method of sentiment analysis in order to examine any quantifiable changes in the linguistic, topical, or narrative patterns that are present in the English-language Islamic State-produced propaganda magazines Dabiq (15 issues) and Rumiyah (10 issues). Based on a sentiment analysis of the textual content of these magazines, it was found that the overall use of language has remained largely consistent between the two magazines and across a timespan of roughly three years. However, while the majority of the language within these magazines is consistent, a small number of significant changes with regard to certain words and phrases were found. Specifically, the language of Islamic State magazines has become increasingly hostile towards certain enemy groups of the organization, while the language used to describe the Islamic State itself has become significantly more positive over time. In addition to identifying the changes and stabilities of the language used in Islamic State magazines, this study endeavours to test the effectiveness of the sentiment analysis method as a means of examining and potentially countering extremist media moving forward.