Early mobilization (EM) of patients in the intensive care unit (ICU) is a safe, feasible, and beneficial approach. However, the implementation of EM as a part of routine clinical care can be challenging. As a result, the present study aimed to identify the potential barriers to EM of ICU patients. The statistical population of this descriptive-analytical study included 107 critical care nurses working in hospitals affiliated with the Jundishapur University of Medical Sciences of Ahvaz. The participants were selected using the census method among the eligible critical care nurses, and the researcher-made questionnaire was used for data collection. This questionnaire included a demographic questionnaire and an inventory of barriers to EM. In total, 72% of the nurses had a highly positive attitude towards EM implementation, whereas relatively few had a slightly positive attitude. The major human-resource-related barriers included the lack of trained staff (76.6%), inadequate shift nurses (74%), and inadequate time for this procedure (57.9%). Approximately 88.9%, 82.2%, 62%, and 57.9% of the nurses reported coma or a deep degree of sedation, mobilization of obese patients, mobilization of patients with agitation, and pain, respectively, as the major patient-related barriers. The lack of EM implementation and recording according to the checklist (90.4%), the lack of an approved EM implementation protocol (88.8%), and inadequate equipment for the mobilization of mechanically ventilated patients (58%) were among the major equipment-related barriers. The participating nurses were aware of the EM advantages, and the majority of them had a highly positive attitude towards its implementation in the ICU. However, nurses believed that the actual EM implementation is associated with challenges such as human resources limitations, equipment-related barriers, and patient-related barriers.