In 1987 Hanna was ordained and served as the pastor of the Gaza Evangelical Church, while he pursued a BA degree from Bethlehem Bible College, which he received in 1991.

Hanna then left Gaza to attend Fuller Theological Seminary in Pasadena, California, where he received his master of divinity degree in 1994 and the PhD in Theology in 2000. While he was studying at Fuller, Hanna served as the pastor of First Baptist Church of Azusa, California. Hanna was called to serve again as the pastor of the Gaza church in 1999.

Besides the normal activities of Christian ministry, such as Sunday worship, regular Bible study, outreach and pastoral care, the Christian Mission to Gaza distributes food and other essentials to as many families, both Muslim and Christian, as its resources allow.