Objective To develop and assess the feasibility of a simplified Spondyloarthritis Research Consortium of Canada (SPARCC) MRI score for quantifying disease activity changes in patients with axial spondyloarthritis (axSpA) undergoing biological therapy, and compare its performance with the original SPARCC score. Materials and methods This prospective feasibility study included 60 axSpA patients receiving biological therapy. MRI examinations of the sacroiliac joints and spine were performed at baseline and six months after the initiation of biological therapy. The simplified SPARCC score, focusing on the three most affected slices/vertebrae instead of six, was developed and compared with the original SPARCC score. Both scores were correlated with clinical indices and inflammatory markers. Inter-reader agreement and sensitivity to inflammatory changes were evaluated to assess reliability and research utility. Results Both scores showed significant improvement after six months of initiating biological therapy (p < 0.001). The simplified SPARCC scores correlated strongly with disease activity markers, comparable to or stronger than the original scores, with median score reductions of 71.4–79.1%. Inter-reader agreement was substantial to almost perfect for all scores, with simplified SPARCC spine score exhibiting the highest agreement (κ = 0.817 at baseline and 0.784 at follow-up). The simplified score significantly reduced assessment time compared with the original score (11 vs 37 min, p < 0.001). Conclusion The simplified SPARCC MRI score is a promising research tool for assessing disease activity in axSpA patients, with the advantages of improved inter-reader reliability and significantly reduced assessment time. Further validation is required to confirm its broader clinical applicability.