Born in 1954 in Zduńska Wola, Andrzej Olejniczak started his musical education at the age of 6. He learned to play the piano, later on reached for a clarinet and a saxophone. In 1976 he graduated with honors from the Academy of Music in Łódź, clarinet class. While studying classical music, he got interested in jazz and jazz-related music genres.

He was a co-founder of Sun Ship group and a member of String Connection – one of the best jazz formations of the last decades. He collaborated with nearly all jazz groups of the ’70s and ’80s, e.g. Extra Ball, Swing Session, Novi Singers, Big Band Katowice, and also Polish Radio Big Band directed by Andrzej Trzaskowski and Zbigniew Namysłowsi, Andrzej Dąbrowski and Sławomir Kulpowicz. As a session musician he has worked with artists such as Józef Skrzek or Maanam.

After leaving for Spain in 1984 Andrzej Olejniczak started working with a world class blind jazz musician Tete Montoliu and for four years he performed with him on stages of many European festivals. In 1986 he performed with Gerry Mulligan at San Remo Jazz Festival, and two years later he played with Kenny Drew Trio at  Festival de Jazz de Lorca-Murcia. Catch (1994), his first independent album recorded in Spain was awarded Record of the Year, and Live At Altxerri (2004) was highly appraised by the „Jazz Forum” magazine.

Andrzej Olejniczak has taken part in countless international projects, performing at almost all festivals in Europe and all over the world (e.g. Milan, Paris, Montreal, San Sebastian, Lima, Marciac, Quito). The artists who he performed with include: Kenny Drew, Randy Brecker Group, Hiram Bullock, Joe Newman, Horace Parlan, Lou Blackburn, Oliver Jackson, NHO Pedersen. He often collaborates with leading Spanish stars of rock and pop music, e.g. Orquesta Mondragón, Mecano, Miguel Ríos, Manzanita, Itoiz, Oskorri, Revolver.

The musician performs also classical music. He has accomplished, e.g. two music projects with Bilbao Symphony Orchestra (1995, 2006), and recorded an album Different Choice (2010) with Apertus String Quartet. In 2013 he performed with the Polish Radio Orchestra directed by Krzesimir Dębski in Witold Lutosławski Concert Studio of Polish Radio.

He lives and works in Spain where he records and gives concerts. He also teaches clarinet and saxophone at Centro Superior de Música del País Vasco „Musikene” in San Sebastian, and at Conservatorio de Leioa.