Spatial ability, defined as the ability to visualize, imagine, translate, and interpret 2D and 3D spatial information, is a crucial building block required for the interior design and architecture professions. In this paper, we report on the development process as well as the validity and reliability of the Architecture and Interior design domain‐specific Spatial Ability Test (AISAT), a new instrument that measures domain‐specific spatial ability in the field of architecture and interior design. A total of 142 college students in Korea and the U.S. engaged in the final stage of the development process—the validity and reliability check—by taking both the AISAT and two general spatial ability tests. The results from the split‐half correlation and internal consistency showed that the AISAT reached a desirable level of reliability. Face, content, concurrent, and convergent validity were achieved to verify the AISAT. The authors hope that the AISAT will be used to measure domain‐specific spatial ability, ultimately expanding our understanding of the role of spatial ability in spatial design thinking and performance. The AISAT has the potential to benefit (1) researchers who seek a credible tool to assess design students' spatial ability, (2) educators investigating the effect of their intervention in spatial design performance in relation to spatial ability, and (3) researchers in spatial ability who would like to extend their interest in spatial design beyond the traditional psychometric approach.