The sisters will lead the U.S. against Belarus in a best-of-five Group II tie in Worcester from February 4-5. The Americans are not in the World Group this year, which means they cannot capture an 18th Fed Cup title.
Venus will play for the first time this year after being sidelined with Sjogren's Syndrome, an incurable autoimmune disease that can cause fatigue and joint pain.
The sisters will play Fed Cup together for the first time in nearly five years.
"I am looking forward to having Serena and Venus on the team for the first time since I became U.S. Fed Cup captain," Fernandez said. "They bring so much to this team, not only for what they can do on court, but the influence they will have on Christina and the rest of the team."
Serena is a 13-time Grand Slam champion, while her fellow former world No. 1 older sister boasts seven major championships.
The winner in Worcester will advance to the World Group playoffs and have a chance to compete for the Fed Cup title next year.