COVID-19 has affected millions of people around the globe. People's mental health, especially those of nurses, has been primarily affected by the fear of this virus. More focus has been paid to vaccination and treatment of the virus, but less attestation has been given to addressing the mental health of people affected by the virus. Empirical studies show that different external factors are not easily manageable and controllable by the individual. This study preliminarily explores the connection between fear of COVID-19 and secondary traumatic stress in nurses. Further, it examines the moderating effects of occupational self-efficacy on the relationship between fear of COVID-19 and secondary traumatic stress. Data for the study was collected from the nurses of six large hospitals in Karachi, Pakistan. The final analysis was performed on 243 samples. Studies on COVID-19 suggest that increased occupational self-efficacy decreases fear and its impact. This study offers insights for managers to develop stress management programs and provide proper training and counseling sessions to the nurses to motivate them emotionally. Theoretically, this study broadens the understanding of the theory of emotions by using the pandemic as a stressor. Future studies may explore different roles of occupational self-efficacy and study its influential role in managing different kinds of emotions explained by the theory of emotions. Managers at the workplace could design different self-efficacy training for nurses to increase their self-motivation to fight different types of stress they face at the workplace.