Background The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is the patient-reported outcome (PRO) that is routinely used in clinical practice to monitor and measure disease activity in axial spondyloarthropathy (axSpA). BASDAI scores greater than four are thought to indicate active disease and require better control. Magnetic resonance imaging (MRI) is the most objective measure of disease activity in axSpA with its ability to pick up active inflammation both in the spine and sacroiliac joints. Previous studies have shown conflicting correlations between BASDAI and MRI, and therefore, there is the question of whether BASDAI is the best tool to monitor disease activity when it is subjective and potentially influenced by other patient factors. We, therefore, conducted a retrospective study to investigate the correlation between BASDAI and MRI in axSpA patients. Methodology Data were collected by retrospective analysis of axSpA patients attending University of Leicester (UHL) axSpA services. BASDAI scores were done within a year and closest to the time of MRI spine + sacroiliac joints were collected. The results prior to the initiation of biologic therapy were used. Data of one hundred and forty-nine patients were collected on their MRI results and BASDAI scores. Data were analysed using Statistical Package for the Social Sciences (SPSS) software and Pearson's chi-squared applied to assess the correlation between BASDAI and MRI findings. Results Out of one hundred and forty-nine patients, 61.7% had active sacroiliitis on their MRI, 57.7% had chronic sacroiliitis, 53% had active spinal inflammation, and 17.4% had other MRI findings of active disease. There was a significant correlation between active sacroiliitis and BASDAI (p=0.014), but similar results were not found with other radiological features. A significant correlation was also found with males having higher BASDAI scores compared to females (p=0.027). Conclusion This study demonstrates a statistically significant correlation between BASDAI and active sacroiliitis with those having higher scores more likely to have active disease on their MRI.