Urban youth in the Global South are critical for climate action, yet barriers to their engagement remain poorly understood. This mixed-methods study of 155 Cairo University students reveals a critical paradox: while a majority demonstrates high climate awareness (50.3% identify human causes; 84.5% deem it a serious threat), this concern fails to translate into action. Our analysis identifies the primary driver of this attitude-behavior gap as a profound crisis of institutional trust. Only 15.4% believe the government is doing enough. This skepticism, compounded by psychological and informational barriers, cripples the perceived efficacy of action. We conclude that in contexts of low trust, strategies must pivot from raising awareness to building collective efficacy through transparent governance and localized communication that empowers youth as agents of change.