Johnston grew up in France, where his American parents started an interdenominational youth movement seeking to introduce Jesus to French teenagers in a non-denominational way. After college (Westmont College, BA in Philosophy), he obtained an MDiv at Gordon-Conwell Theological Seminary and served for nine years as associate pastor in two expatriate churches in Algiers, Algeria. Then he spent another seven years teaching in a language school in Ismailiya, Egypt, and finally at a Palestinian Bible college in Bethlehem, West Bank.
After these sixteen years in the Arab world Johnston turned to academics, earning a PhD in Islamic Studies at Fuller Theological Seminary, which led him to continue research in contemporary Islam in the Religious Studies Department at Yale University. Since 2006 he has been a Visiting Scholar at the University of Pennsylvania, teaching several courses there until 2009, and now serving as an adjunct lecturer at St. htmeph's University. His research and writing has focused on the intersection of law and theology in modern Islamic scholarship and on Muslim-Christian dialogue. Besides a number of articles published in leading academic journals, he is the author of Earth, Empire and Sacred Text: Muslims and Christians as Trustees of Creation (London: Equinox, 2010), and Evolving Muslim Theologies of Justice: Jamal al-Banna, Mohammed Hashim Kamali and Khaled Abou El Fadl (Penang, Malaysia: CenPRIS and Universiti Sains Malaysia Press, 2010).
Johnston is a leader in his local church (Blue Route Vineyard, Media, PA) and a member of Media's Fair Trade Committee, the very first Fair Trade Town in North America. He is actively involved in a wider evangelical movement seeking to address the long history of ignorance and fear, animosity and prejudice between Muslims and Christians. In particular, he regularly contributes blogs to Peace Catalysts International (www.peace-catalyst.net). As a scholar he is an active member of the Study of Islam section of the American Academy of Religion and of the Center for the Study of Islam and Democracy. He is available to speak or teach seminars in churches, mosques and more neutral venues as well.