Pettagrue recieved a degree in philosophy and sociology from Morehouse College in Atlanta, and received his Masters of Divinity from the New Orleans Baptist Theological Seminary. He continued his studies at the University of Alabama at Birmingham, Birmingham Seminary, Morehouse School of Religion, and Emory University.
At his retirement in 1971, Ralph D. Abernathy recommended Pettagrue as pastor of Sardis Baptist Church, who accepted the pastorship that June 12. Under his leadership the church membership rolls grew to more than 3,000. Pettagrue retired in 2006 and was succeeded as executive pastor by Van Moody.
On May 29, 2008, Pettagrue was named in a 48-count indictment by a federal grand jury on charges of conspiracy, mail fraud money laundering and bribery involving his Heritage to Hope Foundation. He was accused of giving kickbacks to state senator E. B. McClain in return for grants that McClain's office secured for the charity. The defendants were convicted on all counts on January 21, 2009. Pettagrue was sentenced 1 year of home detention, $366,000 in restitution, and five years of probation.
- Gordon, Robert K. (January 21, 2009) "Birmingham jury needs only day to convict state Sen. E.B. McClain, Rev. Samuel Pettagrue on 48 counts." The Birmingham News
- Dean, Charles J. (May 19, 2009) "Rev. Samuel Pettagrue of Birmingham given five years probation in federal corruption case." The Birmingham News
- Garrison, Greg (June 17, 2014) "Retired Sardis Baptist Pastor Sam Pettagrue dies; civil rights activist was convicted in kickback scheme." The Birmingham News