He was born on February 13, 1950 to a family of musicians in Ankara, Turkey, where his father was the head trumpeter in the State Philharmonic Orchestra. He continued Kadıköy Anadolu Lisesi which is also commonly known as Kadıköy Maarif College for his high school education in Istanbul following his father's death. After the high school, he attended the State Conservatory in Ankara and graduated in performing arts, in particular (theater).
He started playing the guitar during his high school years. In 1966, Mazhar formed the band Kaygısızlar ("The Carefree") along with Fuat Güner and Sadik Kuyas. They played the music of the Beatles, Crosby, Stills & Nash and the Rolling Stones and collaborated with the renowned Turkish pop singer Barış Manço. Later on, Özkan Uğur joined the band, and in 1972 the trio was renamed MFÖ, after the initials of the members. While Özkan was serving his military duty, Mazhar and Fuat released their first album Türküz Türkü Çığırırız("We are Turkish, we will sing Türkü"). The album song Güllerin İçinden ("From in-between the roses") brought the group to a broader audience. In 1974, Galip Boransu and Ayhan Sicimoğlu joined the band, and the quintet took the name İpucu Beşlisi ("Clue Quintet"). However, the band dissolved after a short time, and the group MFÖ continued to play as a trio again.
Between 1972 and 1982, Mazhar Alanson played as an actor at the Ankara State Theatre, performing a number of leading roles in major plays.
MFÖ represented Turkey in the Eurovision Song Contest twice, in 1985 with Didai Didai Dai (placed 14) and in 1988 with Sufi (placed 15), both written and performed by themselves.
Aside from the band, he released two solo albums: Herşey Çok Güzel Olacak (1999) and Türk Lokumuyla Tatlı Rüyalar (2002).
Mazhar Alanson was awarded the "Best Songwriter of the Year" in 1984 for his album Ele Güne Karşı Yapayalnız
As an actor
He played in several TV commercials and some films. In the film Arkadaşım Şeytan (Demon, My Friend) directed by Atıf Yılmaz, he successfully played the role of Mephistopheles. He wrote also the film score. In his second film Her Şey Çok Güzel Olacak ("Everything's Gonna Be Alright") directed by Ömer Vargı, Mazhar Alanson shared the leading roles withCem Yılmaz and Ceyda Düvenci. The film, he wrote also the film music for, became the highest-grossing movie in 1998. He shared in 2002 the leading role again with Cem Yılmaz in the film Yıldızlı Pekiyi ("A+" (letter grade in school)). The same year, he played in the TV series Çekirdek Aile ("Nuclear family") produced for Kanal D. In 2006 he appeared in the Cem Yılmaz movie Hokkabaz ("The Magician").İngilizce Performans Ödevi