[3] From 1995 to 2018, Willms was Professor of Education at the University of New Brunswick,[4] where for eight years he held the Canadian Institute for Advanced Research Chair in Human Development and for fourteen years held the Tier 1 Canada Research Chair in Literacy and Human Development.

[11] In 2004, Willms co-founded The Learning Bar Inc., with the aim of bringing his research on children's development and assessment into widespread practice.

The company employs over 70 staff in its Canadian and Australian offices, providing research and assessment services in several countries worldwide.

The company's flagship products are the Early Years Evaluation, Confident Learners, and the OurSCHOOL / Tell Them From Me suite of school surveys.

Willms's research contributions span four decades with publications in the areas of child development,[7] children's health,[12] youth literacy,[7] the accountability of schooling systems[13] and the assessment of national reforms.