Background: Resuscitation science has gained significant advancements over the past 60 years. The American Heart Association recommends the use of physiological monitoring to give real time feedback, with the aim of improving the quality of resuscitation performed. Invasive blood pressure measurements and end tidal carbon dioxide levels are currently recommended as first line monitoring methods. However, these methods are either invasive, dependent on an advanced airway and may not always be available. There is a need for a readily available, non – invasive, easy to use device. The perfusion index may serve as such a measure. Objective: To establish an association between perfusion index and return of spontaneous circulation during cardiac arrest. Methods: A cross-sectional observation study was conducted in the intensive care unit of a tertiary level facility. Patients were recruited following a witnessed cardiac arrest, where resuscitation was commenced. A Masimo Signal Extraction pulse oximeter (SpO2) was attached to the patient at the start of resuscitation. The device measured and recorded perfusion index values against a timestamp. Individual patient data were exported as a comma separated variable file to R Core Team® version 4.2.1(2022) for analysis. Corresponding clinical data was collected for each participant. Results: The median time-weighted average (IQR) in perfusion index was higher in those achieving return of spontaneous circulation 0.82% (0.43,1.09) compared to those who did not 0.18% (0.09,0.30), p < 0.001. Furthermore, a time-weighted mean perfusion index of > 0.69% was critical in prediction of return of spontaneous circulation. Conclusion: Perfusion index values were higher in the group which achieved return of spontaneous circulation, compared to the group which failed. Perfusion index may have utility in monitoring the quality of cardiopulmonary resuscitation performed.