His parents are Carolyn and Jim. He is the youngest of three kids. Both of his older brothers played college basketball; Jimmy played at NYU, and Dom played at Northwestern as a walk-on before transferring to St. Thomas.
Nick grew up going to Northwestern basketball camps in the Chicago area. He played at Glenbrook South High in the northern suburbs of Chicago. He broke out as a junior, averaging over 20 points and winning all-state honors. As a senior, he won all-state honors again while leading his high school to a sectional title. Martinelli was a three-star recruit and committed to Elon before his senior season. However, Elon coach Mike Schrage resigned to become an assistant at Duke, and Martinelli decommitted.
He then chose Northwestern over Xavier and Utah. Martinelli earned minutes as a freshman and became a starter near the end of his sophomore season. He averaged 11 points in his last 11 games that season and helped lead the Wildcats to the second round of the NCAA Tournament for the second straight year. As a junior, he averaged over 20 points and won second-team All-Big Ten honors. He returned to Northwestern for his senior season and averaged 23 points, once again making second-team All-Big Ten.
Martinelli is also a high-end student, winning back-to-back first-team Academic All-America honors. He is automatically eligible for the 2026 NBA Draft after having exhausted his collegiate eligibility.
