Abstract: The present study seeks to investigate MNOs leadership style and how it influences their compassion competence and their personal level of compassion at work. This is a cross-sectional study carried out from December 2019 to May 2020 using the method of convenience sampling. The study involved 235 MNOs serving in Greek Military Hospitals. A single questionnaire containing Compassion at Work index, Compassion competence scale, and Multifactor Leadership Questionnaire (MLQ-5X), and socio-demographic and professional data, was used for data collection. A total of 400 printed questionnaires were distributed with a response rate of 58.75%. Data analysis was performed using the statistical package SPSS 22.0. The research showed that the transformational and transactional leadership styles coexist in the Nursing Corps of the Armed Forces with an average value of 2.72(SD=0.70)-2.95(SD=0.54) points and 2.47(SD=0.69)-2.74(SD=0.63) points respectively, while the passive style represented a very small percentage with an average subscale value of 0.88(SD=0.61)-0.94(SD=0.63) points. It was also found that both actual compassion at work and compassion ability had improved with the increase of transformational or transactional leadership style characteristics and amelioration of leadership outcome criteria. On the other side, a deterioration of these was observed with the increase of the passive leadership. Specifically, a higher score in the «Intellectual Stimulation» scale was associated with a higher level of compassion at work in the dimension «Experiencing the suffering of others» (p=0.010/SD=0.14), while higher values on the «Laissez-Faire Leadership» scale were associated with less compassion at work in the same dimension (p<0.001/SD=0.13). Also, a higher score on the «Contingent Reward» scale was associated with more compassion at work in the dimension «Takes appropriate action» (p=0.023/SD=0.16). Furthermore, higher values observed in the «Inspirational Motivation», «Individual Consideration» and «Extra Effort» scales were associated with a better communication ability (p=0.035/SD=0.09, p=0.022/SD=0.12, and p=0.042/SD=0.08 accordingly). Finally, a higher score on the «Effectiveness» scale was associated with higher sensitivity (p=0.049/SD=0.08). Teaching appropriate leadership behavior, promoting a culture of compassion, and continuing to train nurses to manage their emotions should be included in the infrastructure of nursing science.