The purpose of this quantitative study was to identify the perceived self-leadership capacity and behaviors of K-5 principals in the state of Illinois and to establish whether or not there was a correlation between principal self-leadership and student achievement. In order to achieve this overall objective, the following research questions framed this quantitative methods study: (1) What is the perceived level of self-leadership among K-5 Illinois principals? (2) What are the perceived areas of strength in the sub-categories of self-leadership for K-5 Illinois principals? (3) What are the perceived areas of weakness in the sub-categories of self-leadership for K-5 Illinois principals? (4) What is the relationship between perceived self-leadership capacity of K-5 Illinois principals and student achievement? This study utilized a quantitative methodology with a survey and correlation design. K-5 Illinois principals were sent a link to an online survey that included the Revised Self-Leadership Questionnaire developed by Jeffrey Houghton and Christopher Neck. Student achievement data was collected from principals from the 2015-2016 PARCC assessment. This study concluded that the RSLQ is an acceptable instrument for measuring self-leadership with this population of K-5 Illinois principals. The study also revealed that K-5 Illinois principals demonstrate a moderate to high level of overall self-leadership with strengths in the subscales of self-goal setting and self-cueing. K-5 Illinois principals demonstrated weakness in the subscale of self-reward. In addition to the findings on the self-leadership capacity of principals, it was found that there was no correlation between principal self-leadership and student achievement. However, when controlling for a school's socio-economic status there was a weak, yet significant correlation between the self-leadership capacity of the principal and student achievement. This study recommends training for principals in self-leadership strategies as a way to enhance personal and professional effectiveness, particularly on the subscale of self-reward. The study also makes recommendations for future educational research including examining the self-leadership capacity of teachers and district level education leaders. In addition, future research is recommended to explore the behaviors and conditions of principals that demonstrate both high and low levels of self-leadership. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]