Rabbits (Oryctolagus cuniculus) are popular companion species and are often presented for emergency care. Systemic Inflammatory Response Syndrome (SIRS) scoring systems have been used in humans, dogs, and cats to gauge illness severity and estimate prognosis in emergency settings. However, SIRS scoring systems are not available for rabbit patients. The objective of this study was to evaluate the prognostic utility of a rabbit SIRS score to facilitate client communication and guide therapeutic decision-making. Medical records for companion rabbits presenting to the University of Illinois’ Veterinary Teaching Hospital from January 2012 until January 2022 were reviewed (N = 205). Data recorded included signalment, temperature, heart rate, respiratory rate, total leukocyte count (WBC), the presence of band heterophils, and survival to discharge. This data was used to develop five candidate SIRS scores for rabbits, based on feline and canine models. Individual health parameters and composite SIRS scores were tested for association with survival to discharge using general linear mixed models. The presence of band heterophils, hypothermia, bradycardia, and SIRS scores derived from these values were significantly associated with mortality (p < 0.05). However, the best-performing SIRS score had poor sensitivity (37%) for identifying rabbits that died or were euthanized, limiting its clinical utility. It is important for emergency veterinarians to accurately assess the clinical condition and potential prognosis of rabbit patients. This study represents a first step towards improving rabbit veterinary care in an emergency setting, but additional work is needed to optimize prognostication in this species.