Patient-centered care is both a goal in itself and a tool for enhancing health outcomes. The application of patient-centered care in health care services globally however is diverse. This article reports on a study that sought to introduce patient-centered care. The aim of this study is to explore the process of providing patient-centered care in critical care units. The study used a grounded theory method. Data were collected on 5 critical care units in Tehran University of Medical Sciences. Purposive and theoretical sampling directed the collection of data using 29 semistructured interviews with 27 participants (nurses, patients, and physician). Data obtained were analyzed according to the analysis stages of grounded theory and constant comparison to identify the concepts, context, and process of the study. The core category of this grounded theory is "humanizing care," which consisted of 4 interrelated phases, including patient acceptance, purposeful patient assessment and identification, understanding patients, and patient empowerment. A core category of humanizing care integrated the theory. Humanizing care was an outcome and process. Patient-centered care is a dynamic and multifaceted process provided according to the nurses' understanding of the concept. Patient-centered care does not involve repeating routine tasks; rather, it requires an all-embracing understanding of the patients and showing respect for their values, needs, and preferences.