INTRODUCTION: The COVID-19 pandemic has had a significant impact on nursing practice in intensive care unit and consequently, on workload. OBJECTIVE: To assess the nurse-patient ratio required by COVID-19 patients and to identify the factors that influence nursing in this context. DESIGN: This study was a retrospective observational study that evaluated the ratio using the Nursing Activities Score (NAS). SETTING: Three Belgian French-speaking hospitals, including five ICUs. Patients included COVID-19 and non-COVID-19 patients. MEASUREMENTS AND MAIN RESULTS: The study included 95 COVID-19 patients and 1604 non-COVID-19 patients (control group) resulting in 905 and 5453 NAS measures, respectively. The NAS was significantly higher among the COVID-19 patients than in the control group (p = <0.0001). In the COVID-19 group, these higher scores were also observed per shift and uniformly across the three hospitals. COVID-19 patients required more time in the activities of monitoring and titration (χ2 = 457.60, p = <0.0001), mobilisation (χ2 = 161.21, p = <0.0001), and hygiene (χ2 = 557.77, p = <0.0001). Factors influencing nursing time measured by NAS in the COVID-19 patients were age <65 years old (p = 0.23), the use of continuous venovenous hemofiltration (p = 0.002), a high APACHE II score (p = 0.006) and patient death (p = 0.002). A COVID-19 diagnosis was independently associated with an increase in nursing time (OR = 4.8, 95% CI:3.6-6.4). CONCLUSIONS: Patients hospitalised in the ICU due to COVID-19 require significantly more nursing time and need an average ratio of almost 1:1.