Mason joined CBS News as a correspondent in 1986. He was the London Bureau correspondent from 1987 to 1990. From 1991 to 1993, Mason was the Chief Moscow Correspondent. He contributed award-winning coverage of the 1991 Soviet coup attempt from Moscow, Russia. He has been working in New York City since 1993. Mason was named the Business Correspondent in 1998. In early 2012 Mason became the co-anchor of "CBS This Morning Saturday", and in 2019 became a co-host of the popular CBS This Morning weekday program.