This study examined associations between students' participation in sport out of school and their calibration of sport performance in physical education. Four hundred twenty nine fifth and sixth grade students reported their sport participation and performed a basketball shooting test after they had estimated their performance in this test. Two calibration indices, bias and accuracy, were calculated. The results showed that most of the students were overconfident. Sport participants compared to non-sport participants were more accurate in estimating their performance, and sport participation predicted students' calibration accuracy. Accurates reported higher sport participation than overestimators, and overestimators were more within non-sport than sport participants. These results were discussed with reference to calibration and self-regulated learning in sport and physical education.