Study objective: Is erector spinae plane (ESP) catheter insertion within 24 h of hospital admission for rib fractures associated with a lower incidence of respiratory complications compared to those having an ESP within 48 h or after 48 h of admission. Design: Retrospective cohort study. Setting: Hospital. Patients: 199 patients admitted for rib fractures, who received an ESP catheter. Interventions: Timing of ESP performance was assessed by dividing the study cohort into three subgroups: prompt block within 24 h, early block within 48 h and late block after 48 h of admission. Measurements: The primary outcome of interest was the development of respiratory complications. This included pneumonia, pulmonary embolism and respiratory failure. Secondary outcomes included intensive care unit (ICU) length of stay and hospital length of stay. Main results: A prompt ESP within 24 h was performed in 14.5% (n = 29) of patients, 47% (n = 95) received an early block within 48 h and 37% (n = 75) of patients received a late block after 48 h from admission. There was a significantly higher rate of respiratory complications (p = 0.005) with late block. A late block was associated with a significantly longer ICU length of stay (7.82 ± 5.2 days) compared to patients who received an early block (5.84 ± 2.8 days; p = 0.044). There was no significant association with hospital length of stay (p = 0.06). There were no differences between the prompt (within 24 h) and early (within 48 h) block groups for any outcome. Conclusions: The performance of an ESP block after 48 h of admission was associated with an increased incidence of respiratory complications and ICU length of stay. There appears to be no added benefit associated with the provision of a prompt ESP within 24 h.