As the first two decades of the 20th century unfolded, clinical psychologists, who had until then been mainly associated with intelligence testing, attempted to implement a specific psychological method—Carl Gustav Jung's (1875–1961) word‐association “test”—in individual personality assessments. As one of the early clinical psychologists who attempted to use the method, Carl Ransom Rogers (1902–1987) is conspicuously absent from the historiography of clinical psychological testing. In fact, historians have recently suggested that we are lacking narratives about Rogers' early ideas and techniques in the context of both the development of clinical psychology and the emergence of psychological testing as clinicians' foremost scholarly activity. In light of the above, this paper pursues two main goals. First, it attempts to reconstruct Rogers' first original research project on emotional adjustment testing in young children in the broader context of the development of word‐association tests as carried out by Jung and Whately Smith (1892–1947). Second, it aims to reconstruct Rogers' earliest theoretical ideas as well as his epistemological assumptions regarding test objectivity, validity and reliability. By drawing on unpublished documents and heretofore overlooked primary sources I show that although Rogers initially drew from Jung and Smith's complex and refined tradition, he ultimately rejected it as well as the tests themselves. At first drawn to Smith's quantitative, empiricist and experimental philosophy of psychology, Rogers was deterred when the data gathered through his own research in 1927 suggested that word association tests had no real, effective clinical value when used in children. By showcasing the complex process of test construction and validation undertaken by 1920s clinical psychologists, Rogers' case illustrates the research practices, the methodological problems and the epistemological dilemmas faced by most if not all of his contemporaries.