Introduction: Military nurses’ preparedness is directly related to reduced casualties during the crises caused by natural disasters. Determining influential factors for proper planning is one of the main priorities of disasters management. Objective: The present study aimed to investigate nurses’ preparedness and its Related factors when facing natural disasters. Materials and Methods: A total of 305 nursing staff affiliated with medical centers and Aja hospitals in southwestern Iran (2021) were included in this descriptiveanalytical study. Demographic information form and disaster preparedness questionnaire were used to collect data. Data analysis was performed in SPSS Software version 19, and a P-value of below 0. 05 was considered statistically significant. Results: The mean age of nurses was 31. 52± 5. 92 years, and their work experience was 10. 00± 5. 94 years. The majority of nurses was male (57. 4%) and had a Bachelor’ s degree (%78. 7) and had participated in disaster management maneuvers (61. 3%). The mean knowledge of nurses was 11. 93± 3. 69, the attitude was 67. 18± 11. 54, performance was 15. 45± 5. 59, and their total preparedness score was 94. 63± 16. 31, which is average. Marital status (P=0. 016), education (P<0. 001), employment status (P<0. 001), gender (P<0. 001), attending disaster management courses history (P= 0. 035) and having the experience of working in the area of operation (P<0. 001) were the most important variables increasing nurses’ preparedness. Discussion and Conclusion: The preparedness of nurses, as key crisis team, to reduce casualties and proper crisis management must be improved. Furthermore, it is necessary to pay attention to the factors that measure preparedness in planning for more efficiency.