He was admitted acting for dramatic theatre in National Academy for Theatre and Film Arts "Krastio Sarafov" by Prof. Anastas Mihaylov, studied with Metodiy Andonov and Neycho Popov, and graduated in 1971 with Lyubomir Kabakchiev. His professional career began at the Drama Theatre "Nikolai O. Massaltinov" in Plovdiv City, where it recreates the roles of Orpheus in "Sadal and Orpheus" by Ivan Radoev, Romeo in “Romeo and Juliet” and the Proteus of the "Two Gentlemen of Verona" by William Shakespeare, Kutzar in ”Albena” by Yordan Yovkov. Later on the stage of theatre "Sofia" he plays Leontes in "The Winter’s Tale" by William Shakespeare and the Bekov in "Open the hack" by Boyan Papazov. In 1979, he joined the troupe of the "Ivan Vazov National Theatre and among his most popular roles are: Edmund in “King Lear” by William Shakespeare, Count Almaviva in "The Marriage of Figaro" by Pierre de Beaumarchais, the Man in "Assassins" by Stefan Gechev, Pickering in "Pygmalion" by Bernard Shaw, Eric Larsen in "Enigmatic Variations" by Eric-Emmanuel Schmitt, Captain Bryce in "Arcadia" by Tom Stoppard, the Colonel in “Black comedy” by Peter Shaffer, Karl Breznar in "Popcorn" by Ben Elton, Beli in "Larry Thompson" by Dusan Kovachevich, the Old Man in "Fool for Love" by Sam Sheppard, Tom Sargent in "Skylight " by David Hare, Luis Heredia in "Damned Souls" by Dimitar Dimov, Momo in "Mr. Ibrahim and the Flowers of the Koran" by Erik-Emmanuel Schmitt, Bruno Krechmar in" Camera obscura” by Vladimir Nabokov, the Colonel in "The Peach Thief" by Emilian Stanev, Podkaliosin in "Marriage" by Nikolay Gogol.
His role in the monodrama "Mr. Ibrahim and the Flowers of the Koran" brings him the awards "Crystal Angel" at the Festival "Vilunya" in Ukraine, the Grand Prix of "Albamonofest" in Albania, "Gran Prix" of IX International Festival of Monodrama in Bitola, Northern Macedonia, Special prize at the Festival of Fujairah, Arab Emirates and the award of the Festival of the comedy show in Gabrovo.
In 2016, a competition of the Ministry of Culture, Marius Donkin was elected as a General Manager of the "Ivan Vazov" National Theatre.
During this season you can watch Marius Donkin in "Mr. Ibrahim and the Flowers of the Koran", "The Peach Thief".