Background: Sleep loss can impair cognition in healthy adults (Waters & Bucks, 2011). Poor sleepers post head injury (HI) have significantly worse sustained attention than good sleepers post HI (Bloomfield et al., 2010, Sinclair et al., 2013). Aims: The present study explores the relationships between objective and subjective sleep measures and overall cognitive functioning, sustained attention, memory and executive functioning in people with an Acquired Brain Injury (ABI) who are currently participating in inpatient neurorehabilitation. Methods: This study has a correlational design with exploratory between groups analyses. Twenty participants were recruited and their sleep was assessed using a subjective (Pittsburgh Sleep Quality Index; PSQI) and an objective (Actigraphy) measure of sleep. Cognitive tests were completed to determine current cognitive functioning on specific cognitive domains. Results: Self-reported sleep difficulties were associated with better overall cognitive functioning (r=0.46, N=20, p=0.04) and memory domain scores (r=0.50, N=20, p=0.01). No associations were found between Actigraphy and cognitive performance. There were discrepancies between subjective and objective sleep measures in 45% of participants. 67% of participants with discrepancies between sleep measures under reported poor sleep and 33% over reported poor sleep when compared to an objective measure. Exploratory analysis of clearly good and poor sleepers, defined by congruent objective and subjective sleep measures, revealed poor sleepers have significantly better memory cognitive domain scores than good sleepers (t(9)=2.27, p=0.049;d=1.37). Conclusions/Recommendations: The phenomenon of poor sleep and better memory performance may be explained by poor sleepers having better memory for their difficulties post injury than good sleepers or increased awareness of their current sleep patterns because their memory is better preserved. Clinicians should adopt an objective measure of sleep in addition to subjective measures of sleep when assessing sleep difficulties in an inpatient neurorehabilitation population. Patients who do not report sleep difficulties may in fact be experiencing sleep problems that that could impact on their neurorehabilitation schedule.