Magic general manager Rob Hennigan announced the addition on Friday. Details were not disclosed. He is expected to serve as Orlando's third point guard behind Victor Oladipo and rookie Elfrid Payton.
The 33-year-old Ridnour appeared in 61 games last season with Milwaukee and Charlotte. He started the season with the Bucks before being traded to the Hornets in late February.
The 14th overall pick in 2003 the draft, Orlando becomes Ridnour's fifth NBA team. He has career averages of 9.6 points, 4.6 assists and 2.3 rebounds per game.