Early mobilization (EM) is one of few potential protective factors associated with reduced physical disability post-intensive care (PD PIC). However, only 45% of intensive care units (ICUs) in the United States routinely practice EM despite its recognized benefits. To analyze the evidence on the relationship between critical care EM, PD PIC, and environmental factors, using the theoretical lens of the World Health Organization's (WHO's) International Classification of Functioning, Disability, and Health (ICF). The Whittemore and Knafl methodology for integrative reviews and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines were followed. Qualitative, quantitative, and mixed-methods studies (n = 38) that evaluated EM and 1 or more domains of the WHO ICF were included. Quality was appraised using the Mixed-Methods Appraisal Tool. Study characteristics were evaluated for common themes and relationships. The ICF domains and subdomains pertaining to each study were synthesized. Early mobilization was related to improved functioning on the disability continuum of the WHO ICF. Early mobilization was influenced by several WHO ICF environmental factors. Dedicated physical and occupational therapy teams in the ICU, interdisciplinary rounds, and positive family and staff perception of EM facilitated intervention delivery. However, poor staffing levels, negative unit culture, perceived workload burden, and lack of equipment, education, and financial support impeded delivery of EM. Early mobilization is a promising intervention that may reduce PD PIC. However, environmental factors negatively influence delivery of EM in the ICU. Several gaps in EM research limit its acceptability in ICU practice. Existing EM research is challenged by poor methodological quality. Further study is necessary to better understand the role of EM on PD PIC and improve patient outcomes following critical illness.