"Welcome Diego! Every corner of the most beautiful club in the world greets you," the La Plata-based club said.
The former Argentina coach quit his job at Mexican second division outfit Dorados in June for health reasons after just nine months in charge.
His new club, officially known as Gymnastics and Fencing, is currently bottom of Argentina's 24-club Superliga, with just one point from five matches.
Maradona's appointment at Dorados in September had been a surprise, despite his inglorious coaching history since leaving the national team post following the 2010 World Cup.
He also coached second division Emirati side Fujairah.
The former Barcelona and Napoli forward is perhaps best known for guiding his country to victory at the 1986 World Cup in Mexico.