Objective: To explore critical care clinicians’ knowledge, attitudes and perceptions toward early mobilization of critically ill patients in ICUs. Design: A cross-sectional national survey was conducted. From January to August 2020, ICU nurses in 11 hospitals were surveyed by using a questionnaire on the knowledge, attitudes and perceptions of ICU early mobilization. Results: Totally 512 nurses completed the questionnaire. The respondents’ mean score for knowledge of early mobilization was 6.89 ± 2.91. The level of knowledge was good in 2.5% (13/512), fair in 52.3% (268/512). The attitudes toward early mobilization were positive in 31.4% (161/512). In terms of perceived implementation of ICU early mobilization, 42.9% (220/512) of nurses did not believe that this should be a top priority in intensive care. The attitudes of nurses from different ICUs were significantly different (F = 3.58, P < 0.05). The knowledge (7.34 ± 2.78 vs. 6.49 ± 2.97, t = 3.37, P < 0.001) and attitudes (3.82 ± 0.58 vs. 3.52 ± 0.56, t = 5.63, P < 0.001) of nurses who had early mobilization related training were higher than those of nurses who had no training. Conclusions: The importance of early ICU early mobilization is increasingly recognized by critical care providers. However, there is still a gap in the knowledge, attitudes and perceptions of ICU early mobilization among nurses. In future studies, it is necessary to further systematically identify the reasons leading to the gaps in these aspects and implement targeted interventions around these gaps. Meanwhile, more nurses should be encouraged to participate in decision-making to ensure the efficient and quality implementation of ICU early mobilization practices.