Felienne is associate professor at the Leiden Institute of Advanced Computer Science at Leiden University, where she heads the PERL research group, focused on programming education. She also works at the Vrije Universiteit Amsterdam one day a week, where she teaches prospective computer science teachers.

Felienne is the creator of the Hedy programming language, and was one of the founders of the Joy of Coding conference. Since 2016, she has been a host at SE radio, one of the most popular software engineering podcasts on the web. Felienne is the author of “The Programmer’s Brain” a book that helps programmers understand how their brains work and how to use it more effectively. In 2021, Felienne was awarded the Dutch Prize for ICT research.

Felienne is a member the board of I&I, the Dutch association of high-school computer science teachers, and of TC39, the committee that designs JavaScript.