This chapter places the development of Hamas within the context of 9/11 and examines the relationship between the two. More particularly, this chapter explains three significant episodes in Hamas’s trajectory since 9/11: the impact of the ‘war on terror’ on Hamas: how this then affected how Hamas was shunned by the West following its 2006 political participation; and Hamas’s public disagreements with al-Qaeda over its political participation. Ultimately, this chapter will show that while there was neither an ideological nor an operational association between Hamas and the events of 9/11, there were indeed repercussions for how Hamas was perceived, which translated into rejection both from Western governments and fellow Islamic militant movements. In this context, the events of 9/11 and the ensuing war on terror arguably affected the trajectory of Hamas and its development in the Israeli–Palestinian and broader regional context. However, this chapter will also explain how Hamas has sustained itself in this period.