Understanding and measuring self-regulated learning (SRL) in workplace settings is crucial for fostering professional development, yet research on its operationalization and measurement remains limited. This study aims to develop and validate a theory-driven scale for assessing SRL in the workplace, grounded in Pintrich's four-phase model (forethought, planning, and activation; monitoring; control; reaction and reflection). An additional goal is to create and test a short scale for economic use. Therefore, we conducted two studies. After developing the item pool for measuring the four dimensions of SRL, Study 1 used survey data (n = 409) to select the most suitable items and test their initial validity. We also examine whether SRL is best operationalized as a unified construct or using separate sub-constructs. Study 2 is used to validate the scale trough a three-wave survey of employees (n = 416), applying a cross-lagged panel model to explore reciprocal relationships between SRL and related predictors (i.e., mastery goal orientation and self-efficacy). Findings of Study 1 show that SRL can be best measured as a unified construct and can be economically measured with a short scale. In Study 2, a cross-lagged panel model mostly confirms the supposed nomological network of SRL and its predictive relationships. Our research provides a reliable and economic tool for assessing SRL in workplace settings. Future studies should further validate this scale in diverse employee populations and explore its implications for organizational learning and development.