Background: Laboratory turnaround time is a periodic measure for improving hospital services and increasing the quality of care as well as patient satisfaction. The current study aims to evaluate the correlation between TAT and LOS at Al Noor Specialist Hospital ED. It also help policy makers to enhance the quality of services provided by minimizing the root causes of the problem. Methods: The retrospective cross-sectional research design uses ED Health information system data at Al Noor Specialist Hospital. Analysis of all laboratory tests (Hematology and Biochemistry) ordered by ED physicians from 05 October 2018 until 4 October 2019. The Regression analysis tests used to report the correlation in-between two TAT and LOS. The IBM SPSS "Statistical Package for the Social Sciences" version 21 used to generate the result. Result: The total number of ED visits is(181,704) and the average LOS is about 2 hours and most people using the services are the Saudi citizen, male, in 21-40 years old. The second in order is pilgrims of HAJJ and UMRA His more than 21% of visits. The Study indicated that there is a statistically insignificant result and weak relation between TAT and ED length of stay so, the study accepts the null hypothesis. Conclusion: The study has been proven that there is no relation between TAT and LOS. Further research is needed to assess and evaluate time to physician diagnosis with TAT to verify if there is a relation between them.