Rob Walton was born on October 28, 1944, in Tulsa, Oklahoma, the oldest of four children of Sam Walton (1918–1992), cofounder of Wal-Mart, and Helen Walton (1919–2007). He has a younger brother, Jim Walton, and a younger sister, Alice Walton. Another brother, John Walton, died in 2005.

Walton attended The College of Wooster and graduated from the University of Arkansas in 1966 with a bachelor of science degree in Business administration, where he was also a member of the Lambda Chi Alpha fraternity. He received his Juris Doctor degree from Columbia Law School in 1969. Walton is also a trustee at The College of Wooster.

By the time he left Tulsa in 1978, Walton had three children, was divorced from his first wife, and was remarried to Carolyn Funk. He and Carolyn filed for divorce in 2000. He married his third wife Melani Lowman-Walton in 2005.

After graduation, Walton became a member of the law firm that represented Wal-Mart, Conner & Winters in Tulsa, Oklahoma. In 1978, he left Tulsa to join Wal-Mart as a senior vice President, and in 1982, he was appointed vice chairman. He was named chairman of the board of Directors on April 7, 1992, two days after his father's death.

Along with his siblings, he has pledged about $2 billion to the Walton Family Foundation from 2008 to 2013.

He is ranked at #17 on the 2013 Forbes list of world billionaires with a net worth of $26.1 billion. On the 2013 Forbes 400 list of the richest people in America, he is ranked at #9.