The 33-year-old former Kaizer Chiefs and Mamelodi Sundowns midfielder last played for Cape Town City but left before their unsuccessful play-off promotion bid.
Hope, who have three points from their opening two games of the current season, have already signed a number of experienced campaigners, including Samkelo Zwane, Ayanda Patosi, Craig Martin and Ruzaig Gamaldien.
Part of a Hope statement read: "Keagan Dolly is red. A player who needs little introduction.
"Keagan Dolly brings years of experience at the highest level, both locally and abroad, along with the quality and ability we all know he possesses.
"We're excited to welcome Keagan and his family to the Immortals and to provide him with the platform to enjoy his football, express himself and be the best version of the player we know he can be.
“Welcome to the Immortals, Keagan.”
