Marin Cazacu studied the cello at the "Dinu Lipatti" High School of Music in Bucharest, then at the Ciprian Porumbescu State Conservatory with the renowned teachers Serafim Antropov and Aurel Niculescu. He studied in Weimar with Professor Mezö Lászlo. Marin Cazacu is a laureate of international competitions in Geneva, Markneukirchen, Leipzig, Bologna and Belgrade.

Since 1983, he has been concert soloist of the George Enescu Philharmonic and performs intensively both in Romania and throughout Europe, Asia and the Americas, under the baton of great conductors such as Ghennadi Rojdestvenski, Sergiu Comissiona, Cristian Mandeal, Lu Jia, Nanse Gum, Horia Andreescu, Antoni Ros Marba, Mendi Rodan, Misha Katz, Jean Périsson. He performed in various chamber ensembles with prestigious artists such as Valentin Gheorghiu, Vladimir Orlov, Radu Aldulescu, Viktor Tretiakov, Ilia Grubert, Mihaela Martin, Mirel Iancovici, Silvia Marcovici, Jeremy Menuhin, as a member of the Pro Arte trio and collaborator of the Voces quartet. His name has often appeared on the posters of big important festivals, such as those in Berlin, Bratislava, Bucharest, Hong-Kong, Macao, Munich, Milan, Mateus, Osaka, Singapore, Seoul, Sofia, Tokyo, Valencia, Venice. Marin Cazacu plays a cello Lorenzo Ventapane (1820).

Since 1992, Marin Cazacu has been a professor at the National University of Music in Bucharest, his students successfully asserting themselves on stages in the country and abroad. In 1998 he founded the Cellissimo quartet, together with Alexandra Guțu, Răzvan Suma and Olga Mănescu, and with his students he gives recitals and tours in the formula of 8 to 20 cellos in the Violoncellissimo formation, the record being reached in the orchestral formula of 100 cellos.

In 1999, Marin Cazacu founded the "Enescu and world music" International Festival, which takes place every summer in Sinaia, around the anniversary of the great musician's birthday (August 19, 1881). For the organization of this festival and the establishment of the first national youth orchestra (the Romanian Youth Orchestra, under the baton of Cristian Mandeal), he was awarded numerous prizes, including the Actualitatea Muzicală, Radio Romania Cultural, Constantin Brâncoveanu Prize and the "People of Time" Prize . In 2006 he obtained the title of Doctor of Music with Summa cum laude, in 2017 he received the Order of the Star of Italy and in 2019 he received the national Order "For Merit" in the rank of Knight, awarded by the President of Romania.

His recordings for Electrecord, Olympia, BMG, Casa Radio and AIX Records are testimony to the qualities of this "excellent musician", as Ghennadi Rojdestvenski called him. Everywhere his appearances were enthusiastically commented by the public and the press.

Starting from 2008, he developed the project of the National Youth Orchestras of Romania, which currently includes the Romanian Youth Orchestra, the National Symphony Orchestra of Romania, the Sinfonietta Orchestra and the Junior Orchestra.

In the period 2014-2022, he was the manager of the National Art Center "Romanian Youth" and a member of the leadership of the European Federation of National Youth Orchestras.

From April 2022, he is the manager of the "George Enescu" Philharmonic in Bucharest.