Rinaldi takes over the American team that hasn't won the trophy in 16 years despite holding the all-time record of 17 Fed Cup titles. The Americans reached the finals in 2010, 2009 and 2003 but lost.
Fernandez resigned two months ago after eight years in charge of the team.
"This is an unbelievable opportunity, and I am incredibly excited and honored to take on the position of US Fed Cup captain," Rinaldi said Thursday.
The 49-year-old Rinaldi's coaching debut will come at home in February against Germany.
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Rinaldi takes on an expanded role that includes extra duties like looking after the USTA's player development program.
Rinaldi was ranked as high as number seven in the world in singles in May 1986. She reached the semi-finals of Wimbledon in 1985 and the quarter-finals of the French Open in 1981 and 1986.