Although a substantial body of research argues that women provide terrorist organizations with important tactical benefits, few studies draw out the implications of this argument or examine whether female recruits affect the outcomes of terrorist operations. Using data on individual suicide attacks from 1985 to 2015, I show that an attacker’s gender influences the lethality of an attack. However, this effect is conditional upon the gender norms of the state in which the attack occurs. The results demonstrate that a female advantage is more apparent only in societies where a woman’s role in public life is limited; attacks by female suicide attackers are more deadly in countries where women are largely absent from the workforce, civil society, and protest organizations. I also assess whether counterterrorists eventually adapt to the use of female suicide terrorists. The results demonstrate that female attack lethality is declining with time, suggesting that security forces eventually adapt to women’s participation in terrorism. These findings are consequential because they highlight the effect of persistent gender biases on counterterrorism efforts.