His parents were both immigrants and his brother is John Gabrieli, PhD, a Professor of Brain and Cognitive Scientists at the Massachusetts Institute of Technology[5] with whom he has collaborated on research in education in recent years.

Gabrieli began his first career in entrepreneurship as the co-founder of and CEO of a healthcare informatics company called GMIS which was eventually purchased by industry leader McKesson HBO, where its products continue to be sold and used.

In 2000, he left Bessemer to focus on education policy and innovation but remained affiliated as Partner Emeritus with the firm until 2015 when he fully retired.

[6] In 2008, he authored (with co-author Warren Goldstein) the book Time to Learn: How a New School Schedule is Making Smarter Kids, Happier Parents and Safer Neighborhoods, published by Jossey-Bass.

Gabrieli became involved in politics with a 1998 campaign for the Democratic primary in the Massachusetts's 8th congressional district, ultimately won by Mike Capuano.