The measurement of K-12 students’ scientific creativity has become a key focus of recent research. However, it is a lack of feasible assessment tools for it. This study aims to develop a Scientific Creativity Assessment Tool (SCAT) tailored for K-12 students. The tool is based on ten science contexts aligned with the current scientific knowledge, covering biology, chemistry, geography, physics, and interdisciplinary sciences. It includes 14 questions, dividing into two types: problem-finding items and problem-solving items. The assessment evaluates both divergent and convergent thinking as key indicators of scientific creativity. Data were collected from 52 Chinese elementary school students. The results indicate that: (1) The tool demonstrates good item discrimination; (2) The overall reliability is 0.97; (3) The structural validity is robust; (4) The criterion-related validity analysis reveals significant positive correlations between the assessment dimensions and the fluency, flexibility, and originality of the Runco Creativity Assessment Battery (rCAB). These findings suggest that the SCAT is a reliable and objective instrument for assessing scientific creativity and provides a solid foundation for future research in this area.