There is widespread interest in how cognitive reasoning is used in expert professional practice. However, little is known about the cognitive reasoning in relation to a property valuer decision making. This study utilised the CTA to identify and describe, the cognitive reasoning of property valuers during a valuation task. Six subjects (comprising two expert valuers, two intermediate valuers and two novice valuers) undertook a valuation of a commercial property in a simulated context while thinking aloud. Verbal protocol reports were transcribed and coded using a deductive method. Content and event-sequence analysis yielded the varied knowledge states that valuers of different level of expertise prioritised and the cognitive processes used to operationalised these knowledge states. Further mapping of thought sequence indicated that expert and intermediate valuers had better and well-structured patterns of thought which demonstrate greater degrees of cohesiveness and interrelatedness between cognitive processes. Expert and intermediate valuers used cognitive processes centred on data interpretation and meta-reasoning activities initially to schedule valuation analysis or establish valuation strategies, and latterly to re-interpret and diagnose previously acquired information to update the outcome of their past valuations. Novice valuers’ processes of solving the valuation problem show fewer linkages between cognitive processes, suggesting underdeveloped cognitive structure and quick disengagement from task. The methodology used for recording, analysing and interpreting verbal protocol reports of valuers is shown to be capable of providing insights on cognitive processes, which is useful for research on practitioner expertise and its development.