Numbers and operations is widely considered the most essential domain in elementary school grades. Nevertheless, elementary students in Indonesia have consistently performed unsatisfactorily on this domain in several international mathematics assessments. This study examined 308 Indonesian sixth grade students' current performance(s), misconception(s), and confidence level(s) on a three-tier test containing 40 number sense-related questions. The results showed that most of the students performed unsatisfactorily (indicating low number sense) with a relatively high level of confidence and exhibited considerable misconceptions. The percentage of the correct responses (i.e. answers and reasons) was approximately 46.48% for the 40 questions. Specifically, only 25 students (8.12%) had good number sense, while 60.71% of the students held either strong or moderate misconceptions. The students' strong misconceptions were identified. In addition, other remarkable findings are presented and discussed. Furthermore, the implications of the results and the suggestions for future research are described.