The objective of this study was to develop and test a competency scale, which measures the competency of interprofessional collaborative practice of health professionals. A total of 32 health professionals were interviewed, and then an item pool of 255 items was created to measure the competency of interprofessional collaboration. A questionnaire study was conducted with 1552 health professionals from four different hospitals located in the Kanto region of Japan. The questionnaires were distributed and collected by gatekeepers in each section. The valid response rate was 62.6%. There were a total of 65 questionnaire items measuring the competency of interprofessional collaboration. Each item was assessed by the number of valid responses, distribution of scores, item-total correlation analysis and good-poor analysis. Construct validity was assessed using factor analysis and the relationships among the total scores of each factor with interprofessional education experience during education before and after graduating. Moreover, Cronbach's alpha coefficient was calculated to assess reliability. Finally, 30 items were excluded, and a scale for interprofessional collaborative competency comprising 35 items and 6 factors was developed. From the perspective of construct validity and internal consistency, the scale in its pilot form shows some promising aspects.