Grenz earned his Doctor of Theology degree at University of Munich in Germany under the supervision of theologian Wolfhart Pannenberg. He was ordained to pastoral ministry on June 13, 1976. He later worked within the local church context as youth director and assistant pastor (Northwest Baptist Church, Denver, Colorado, 1971-1976), pastor (Rowandale Baptist Church, Winnipeg, Manitoba 1979-1981), and interim pastor on several occasions. He served on many Baptist boards and agencies and also as a consulting editor of Christianity Today.

While in the pastorate (1979-1981), Grenz taught courses both at the University of Winnipeg and at Winnipeg Theological Seminary (now Providence Seminary). He served as Professor of Systematic Theology and Christian Ethics at the North American Baptist Seminary, Sioux Falls, South Dakota from 1981-1990. For twelve years (1990-2002), Grenz held the position of Pioneer McDonald Professor of Baptist Heritage, Theology and Ethics at Carey Theological College and at Regent College in Vancouver. After a one-year sojourn as Distinguished Professor of Theology at Baylor University and George W. Truett Theological Seminary in Waco, Texas (2002-2003), he returned to Carey in August 2003 to resume his duties as Pioneer McDonald Professor of Theology. In fall 2004, he assumed an additional appointment as Professor of Theological Studies at Mars Hill Graduate School, Seattle, Washington. From 1996 to 1999 he carried an additional appointment as Professor of Theology and Ethics (Affiliate) at Northern Baptist Theological Seminary, Lombard, Illinois.

Grenz' primary contributions were made discussing how evangelical Christianity ought to relate to the world. He wrote on a wide range of subjects, from sexuality to history to basic apologetics, and was one of North America's leading evangelical voices in the late 20th century and early 21st century.

Married to Edna Grenz, a church musician, Grenz was the father of two children, Joel Grenz and Corina Kuban, and was grandfather to one grandchild, Anika Grace Kuban. Included in two editions of Who's Who in Religion, as well as in the 2002 edition of Who's Who in U.S. Writers, Editors and Poets, Grenz died in his sleep March 11, 2005 from a brain aneurysm.