Niklas 'Nicholas' Mustelin was born in Helsinki, Finland in 1966. At age 6 he began piano lessons with Inge-Britt Åkerblom. At 15 he started playing professionally with Finnish jazz musicians such as Nalle Lindström.

After high school he started studies at the Helsinki Pop & Jazz Conservatory. His teachers included Kaj Backlund, Laszlo Süle and Jasse Varpama. In 1993, Nicholas received a Diploma in Performance from Manhattan School of Music in New York City, NYC. His teachers were Harold Danko (piano) & Harvie Swartz (bass). In NYC he performed with musicians including Wynton Marsalis, Ralph Lalama and Ron McClure.

Nicholas graduated from Helsinki Pop & Jazz Conservatory in 1995 with a BA in Music Education. Later that year he moved to Boston, where he studied at Berklee College of Music and graduated with a BA in Professional Music, focusing on composing, arranging and performance.

Nicholas has also studied at the New England Conservatory in Boston and at The Juilliard School in NYC.