Radonjić was born in Gornji Milanovac, SR Serbia, SFR Yugoslavia, where he finished an elementary and a high school.

[1] In the 2007–08 BLS season, Radonjić worked for Swisslion Vršac as a strength and conditioning coach.

[6] In November 2020, Radonjić joined the coaching staff of Partizan led by Sašo Filipovski.

[2] In July/August 2009, Radonjić was a conditioning coach for the Serbia national under-18 team that won a gold medal at the FIBA Europe Under-18 Championship.

[6] Radonjić worked for women teams Rabita Baku (2013–2014), Volero Zürich (2014–2017), and Cannes (2017–2019).