This study aimed to construct and validate a quantitative measurement instrument to determine the structure of professional agency in working life. Empirical data (N = 589) were collected via a web-based, theoretically informed questionnaire, within the professional domains of education, healthcare, rescue services, and information technology. The questionnaire items incorporated theoretically based dimensions of professional agency. The structure of professional agency was initially analysed via exploratory factor analysis. Thereafter, using exploratory structural equation modelling, the structure of professional agency was investigated with a view to confirmation and validation. The results indicated that the structure of professional agency included three dimensions: Influencing at Work, Developing Work Practices, and Negotiating Professional Identity. These dimensions appeared to be separate from but closely linked to other work-related constructs, notably Learning at Work and Emotionally Meaningful Work. The study enriches current theory on professional agency by shedding light on its multidimensional structure. In presenting an instrument for measuring professional agency, the study can benefit scholars and work organisations with an interest in researching and fostering professional agency in various work and educational contexts.