Army senior leaders believe in preparing for future conflicts; the Army must shape future leaders' knowledge, skills, and attributes through rigor and critical thinking in professional military education. The problem addressed by this study was understanding Army senior leaders' perceptions concerning the appropriateness of rigor and critical thinking levels in professional military education. The purpose of this convergent parallel mixed methods research was to explore perceptions of the amount of rigor and critical thinking levels in professional military education as experienced by Army senior leaders to improve the curriculum for future leaders. This convergent parallel study concurrently integrated quantitative and qualitative research methodology. In design and analysis, the incorporation of Knowles's adult learning theory and Kolb's experiential learning theory served as a guiding theoretical framework. The study consisted of 112 Army senior leaders, where a subset of 10 conducted semi-structured interviews and the remaining 102 completed an online survey. Quantitative data were examined by multiple regression analysis that tested hypotheses related to predictive relationships between the dependent variable (i.e., perception) and two independent variables (i.e., rigor and critical thinking). The quantitative analysis revealed that the 102 participants believed rigor levels were significantly higher than critical thinking levels in professional military education. In contrast, qualitative data were examined by a thematic analysis system that analyzed the narrative data from the semi-structured interviews. The primary perceptions categorized by theme were experience, rigor, and critical thinking. The qualitative analysis revealed that the 10 interview participants viewed critical thinking as higher than rigor levels in professional military education. Implications from this study could quickly adjust requirements in the professional military education curriculum to improve leader preparation for operationally complex environments. Supported by thematic analysis and multiple regression analysis, the core recommendation was that the Army urgently should re-evaluate how they measure rigor and critical thinking levels. Overall, each Army senior leader's individual experiences impacted their perceptions of rigor and critical thinking levels in professional military education. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]