Abstrak: Studi ini menganalisa respons organisasi Al-Ittihadiyah di Sumatera Utara terhadap radikalisme. Belakangan ini muncul pernyataan yang menimbulkan kontra produktif di mana organisasi Islam selain Nahdlatul Ulama diragukan perannya dalam membangun peradaban bangsa. Artikel ini menganalisis respons Al-Ittihadiyah terhadap radikalisme. Al-Ittihadiyah didirikan sebelum Indonesia merdeka dan para tokohnya ikut memperjuangkan dan mempertahankan kemerdekaan. Data studi ini diperoleh melalui wawancara mendalam yang dilengkapi dengan kegiatan studi dokumen dan observasi; lalu dianalisis dengan menggunakan model analisis data Miles dan Huberman. Hasilnya adalah bahwa Al-Ittihadiyah merupakan organisasi Islam moderat sebagaimana dua organisasi Islam papan atas, NU dan Muhammadiyah. Organisasi ini, melalui lisan dan tulisan pengurusnya, menegaskan bahwa radikalisme bertentangan dengan semangat Islam. Mereka menolak banyak gagasan kelompok radikal seperti khilafah, anti-Barat, jihad berarti perang, dan legalisasi bom bunuh diri, sembari memberikan solusi bagi peredaman pertumbuhan dan perkembangan radikalisme di Indonesia. Abstract: Al-Ittihadiyah in North Sumatra and Its Responses to Radicalism. This study analyzes the response of the Al-Ittihadiyah in North Sumatra to radicalism. Lately there has been a counter-productive statement undermining the contribution of Islamic organizations other than Nahdlatul Ulama in building national civilization. Al-Ittihadiyah was established in Medan before Indonesia’s independence and its prominent leaders participated in gaining and maintaining independence. Information for this article has been gathered through combination of interviews, observations, and document reviews. Data analysis was based on the model developed by Miles and Huberman. It is concluded that Al-Ittihadiyah is a moderate Islamic organization, very much like the two top-flight Islamic organizations, Nahdlatul Ulama and Muhammadiyah. This organization, through oral and written statement of the management, asserted that radicalism is against the spirit of Islam. They reject many of the ideas of radical groups such as the Caliphate, anti-West, jihâd means war, and the legalization of suicide bombings, while providing solutions to suppress the growth and development of radicalism in Indonesia. Kata Kunci: radikalisme, jihad, kafir, bom bunuh diri, Al-Ittihadiyah, Melayu, Mandailing