This study examines the effects of the effectiveness of the internal control system (ICS) on crisis management skills (before, during, and after the crisis) in the event of a disaster through the Istanbul Metropolitan Municipality (IMM) Fire Service Department. Methodologically, a comprehensive survey questionnaire was used to collect data from 251 workers of the IMM fire service department located on the Anatolian side of Istanbul. Statistic Package for Social Sciences (SPSS) version 22 used to analyze data by running among other reliability tests, T-Test, ANOVA, and Regression analysis. The results of the study indicated that ICS of the Fire Service Department of IMM showed high levels of effectiveness in the event of a disaster and that the institution has a high level of crisis management skills. In addition, the study found that a high positive relationship existed between ICS and Crisis Management Skills of the IMM fire service department before, during, and after the crisis in the event of a disaster. Finally, the study revealed that, ICS has a positive and high impact on IMM crisis management skills before, during, and after the crisis, and that the effectiveness of ICS had increased the crisis management skills of the institution.