He was appointed by Governor Rick Perry on August 24, 2005 to serve out the remainder of former Justice Priscilla Owen's term following her appointment to the United States Court of Appeals for the Fifth Circuit. Willett was elected to a full six-year term on November 7, 2006.
Reportedly, Perry had considered appointing Willett to an earlier vacancy on the court. A suggestion that he would be appointed to fill a vacancy, in late 2004, caused the Houston Chronicle to editorialize against making Willett the nominee at the time.
Willett's first majority opinion was Willis v. Donnelly, which was released on June 2, 2006. Willett wrote for a unanimous court in a case dealing with shareholder liability in close corporations.
Willett, a native Texan, received a triple-major BBA from Baylor University. He received his J.D., along with an M.A. in political science, from Duke University in 1992. After law school, Willett clerked for Judge Jerre Williams at the United States Court of Appeals for the Fifth Circuit. In 1996, He joined George W. Bush's administration when he was Governor of Texas. Willett worked for the Bush-Cheney 2000 Presidential Campaign. Upon Bush's election to the Presidency in 2000, Willett followed Bush to the White House and helped create the Office of Faith-Based and Community Initiatives, where he was Director of Law and Policy. Willett was a Deputy Attorney General for the U.S. Department of Justice in 2002, but he left to join Texas Attorney General Greg Abbott's office in 2003, where he worked until his appointment to the Texas Supreme Court.
Willett and his wife, Tiffany, have two children.
Willett is mentioned in David Kuo's book, Tempting Faith: An Inside Story of Political Seduction ISBN 0-7432-8712-6 (2006), which takes a decidedly negative and critical view of the Bush administration and the Office of Faith-Based and Community Initiatives.
The road to a full term on the Texas Supreme Court in 2006 was a difficult one for Willett, as he faced close calls in both the primary and general election. Former Texas Supreme Court Justice Steven Wayne Smith sought to regain a seat on the court by triumphing over Willett in the Republican primary. Willett narrowly defeated Smith in the contest on March 7, 2006, garnering 50.5 percent of the vote to Smith's 49.5 percent, a difference of about 5,000 votes.
Willett then defeated Democratic Party nominee Bill Moody in the November 7, 2006 general election. Willett won with 2,121,985 votes for 51 percent of the vote versus Moody's 1,873,252 votes for 45 percent.