In recent years, negativity has become a dominant theme in the political campaign. However, there are no comprehensive studies to measure the amount of negativity and to examine how parties and candidates adopt these negative strategies, particularly in the Canadian context. Although some studies have focused on a particular aspect of negative campaigning in a Canadian election, the question remains of how and to what extent parties adopt negative strategies in an election. In this thesis, I have collected and analyzed parties’ press releases in the 2015 federal election to examine and explain negativity in parties’ political campaigns. I have tested my results according to five primary theories of negative campaigning, including competitive positioning, ideological proximity, party organization, coalition or minority effect, and negative personalization, to see if these theories apply in the Canadian context. My results indicate that the 2015 federal campaign was a highly negative one, and most of the negative attacks have been directed towards the leader of the Conservative Party, Stephen Harper, while the Conservative Party published the least amount of negative attacks during the campaign. I also found that the Liberal Party has published the most negative statements during the campaign. My results also show that one of the influential factors in shaping parties’ negative campaign strategies is the other parties’ status in public opinion polls, particularly the federal voting intention factor. Although the results show that most of the attacks in the 2015 campaign targeted leaders of parties, I did not find enough support in my models to verify the negative personalization theory. The overall findings of this thesis show that Canadian elections are moving toward a presidential-style campaign, similar to the United States, by becoming more negative and more personalized, which can have significant implications for Canadian democracy.