Tim was born in 1955 in Littlefield, Texas, and grew up in Big Spring, Texas graduating from Big Spring High School in 1974. He graduated from Texas Tech University in 1978 with a B.S. in Chemical Engineering. Upon graduation Dunn worked at Exxon Production Research Company (1978-1980). He then went on to First City Bancorp (1980-1987) and served as an Engineer and Manager of Oil & Gas Portfolios. He then joined Parker & Parsley Petroleum (1987-1995) where he became a founding general partner of Parker & Parsley Development which later became Pioneer Natural Resources. He held multiple positions including Director, Executive Vice President and Chief Financial Officer. In 1996 he co-founded a private oil and gas concern.
Currently, Dunn is CEO of CrownQuest Operating, LLC, and CrownRock LP.
Dunn is the chairman of the board of directors of Empower Texans and Texans for Fiscal Responsibility. He is also vice chairman of the board of directors at the Texas Public Policy Foundation. He is a founder of Midland Classical Academy, where he serves on the Board of Trustees. Dunn also serves on the board of directors for the following organizations:
Dunn and his wife have six children and eleven grandchildren. The Dunns are active members of Midland Bible Church.