Early enteral nutrition (EN) initiation is recommended for intensive care unit (ICU) patients; however, the optimal rate of EN advancement remains unclear. We aimed to assess the association between EN advancement and in-hospital mortality, as well as length of hospital stay. We performed a retrospective cohort study on 341 critically ill adults receiving EN between January 2021 and December 2023. The exposure of interest was rapid EN advancement, defined as an EN change exceeding the median value calculated between the first and seventh days after EN initiation. The comparator group included patients without rapid EN advancement. Factors related to in-hospital mortality and length of hospital stay were assessed using multivariable logistic and linear regression analyses. Subgroup analyses were performed for EN initiation within 48 h of ICU admission. Rapid EN advancement reduced in-hospital mortality (adjusted odds ratio [OR] = 0.64, 95% CI 0.38-1.07, P = 0.092), although this was not statistically significant. However, rapid EN advancement significantly shortened hospital stay by 25 days (95% CI -25 to -9.2, P = 0.002). In the early EN initiation subgroup, rapid EN advancement significantly reduced in-hospital mortality (adjusted OR = 0.42, P = 0.039) and shortened hospital stay by 48 days (95% CI -77 to -19, P = 0.001). Rapid EN advancement reduced in-hospital mortality and length of hospital stay in critically ill patients, especially with early EN initiation. These findings could inform clinical practices that enhance timely and adequate nutrition therapy in ICUs. Further randomized controlled trials can help establish clinical guidelines.