The purpose of this study is to develop and validate an 18-item Problem-based Learning Process Inventory (PBLPI) for learning in this 21st century. Preservice teachers at the National Institute of Education (NIE) doing Educational Psychology are exposed to a Problem-Based Learning (PBL) environment. Findings from Exploratory Factor Analysis of 1,041 preservice teachers provided evidence for a three-factor solution -- Problem Posing, Scaffolding and Connecting. Results from Confirmatory Factor Analysis of 1,029 preservice teachers provided additional support for the results obtained from Exploratory Factor Analysis. Moderate to high reliability coefficients for the PBLPI scores demonstrated PBLPI as a reliable and valid instrument to measure learners' perception of the key PBL processes.