Williams, 56, was dropped from his job as news anchor of NBC's flagship "Nightly News" program in June after an internal investigation established he had exaggerated various events involving his reporting from the field.
NBC and MSNBC are units of Comcast Corp.
A representative for NBCUniversal said Williams will take up his new job on Sept. 22, the day Pope Francis begins his first visit to the United States, ending a six-month suspension.
Williams had been the face of NBC until he was suspended in February for fabricating a story about being on board a helicopter that was shot down in the Iraq war. The internal investigation found other instances of what it called "inaccuracies" but did not give details.
In a June interview, Williams blamed his ego for the exaggerations and described his suspension as "torture."