Introduction: Studies prove that spiritual practices improve mental health, quality of life, and people's interpersonal relationships. For health professionals, this enables better coping with stress at work with consequential improvement in well-being and greater satisfaction. This study sought to verify if the religiosity/spirituality of health professionals influences upon the care provided to critical patients. Materials and Methods: This was a cross-sectional study with quantitative approach conducted with 53 professionals working in Adult Intensive Care Units of a city in the interior of Brazil. An adapted questionnaire was used along with the Spirituality Self-Rating Scale, and a descriptive and association analysis was performed of the data by using Fisher's exact test with 5% significance level. Results: It was found that 77.4% of the sample was female, with a mean age of 37 years, average time of service of 11 years and most were evangelical/protestant. Most of the professionals reported high spirituality and stated that their religiousness/spirituality strongly influences the understanding of the health-disease process and its relation with critical patients, besides modifying the way of caring for these patients. Discussion: Several studies have shown that religiosity/spirituality can generate calm and tranquility, improve physical and mental health, promote healthier behaviors and lifestyles, decreasing stress and improving interpersonal relations. Conclusions: The religiosity/spirituality of professionals who work in the Intensive Care Unit influences the care provided to critical patients.