Fallon will host on Dec. 17 with Michael Bublé returning for his second time as the musical guest.
"I've never forgotten where I came from. That's why I'm so incredibly honored to be hosting the Saturday Night Times program ... on HGTV," Fallon joked.
Fallon was a cast member on the sketch comedy series for six years, most notably co-anchoring "Weekend Update" with Tina Fey. In 2009, he became the host of Late Night with Jimmy Fallon.
The 37th season of SNL premieres Sept. 24.