To investigate how effectively systemic immune-inflammation index (SII) and Monocyte-to-HDL-cholesterol ratio (MHR) predict the development of early cardio-cerebral complications in elderly patients who have experienced acute severe carbon monoxide poisoning (ASCMP). A retrospective analysis was conducted on 77 elderly patients with ASCMP admitted to the emergency department of Harrison International Peace Hospital from November 2020 to March 2022. The prevalence of early-onset complications among the 77 individuals was 38.96%. Binary Logistics regression analysis showed that SII and MHR were independent influencing factors of early cardio-cerebral complications in elderly patients with ASCMP. The complication group had a longer length of stay, a greater mortality rate, and a higher incidence of delayed encephalopathy after acute carbon monoxide poisoning (p < .05) than the non-complication group. The area under the curve (AUC) of SII and MHR in predicting early cardio-cerebral complications in elderly patients with ASCMP were 0.724 and 0.796, respectively, with 80.0% and 63.3% sensitivity, and 61.7% and 87.2% specificity. The incidence of early cardio-cerebral complications in elderly patients who had ASCMP is high and the prognosis is poor. SII and MHR can be utilized as independent predictors of early cardio-cerebral complications in elderly patients with ASCMP, allowing doctors to diagnose and treat cardio-cerebral complications earlier and improve prognosis.