The present study explored the associations among several cognitive and creative abilities and expert ratings of jazz improvisational quality. Ten male undergraduate jazz students (8 performance majors, 2 education majors; 5 winds, 3 strings, 1 piano, and 1 drum) performed a video-recorded improvisation with a trio and completed measures of divergent thinking, working memory, and fluid intelligence. Performances were rated for creative quality by 3 expert raters. Students also answered questions regarding their musical background and subjective experience of improvisation. As expected, cumulative practice hours substantially predicted improvisational creativity. Results for the cognitive variables showed mostly negative correlations with improvisation; however, divergent thinking strongly predicted performance quality. We consider these results in the context of the literature on expertise and creativity.