Purpose <p>To investigate the asymmetrical sacroiliac joint degeneration (SIJD) in degenerative lumbar scoliosis (DLS), and to evaluate the correlation between SIJ degeneration, spinopelvic parameters and clinical outcomes.</p> Methods <p>We retrospectively reviewed 183 DLS patients. Preoperative measurements were measured on full-length plain radiographs. Backlund’s protocol was used to assess SIJD on CT scans. Patient-reported outcome measures (PROMs) including the Visual analogue scale for back pain (VAS-BP) and leg pain (VAS-LP), Oswestry Disability Index (ODI), and Scoliosis Research Society-22r (SRS-22r) were recorded at baseline. Correlation analyses were performed to investigate the relationship between the SIJD and spinopelvic parameters and between the SIJD and PROMs.</p> Results <p>SIJ degeneration was more severe on the convex side than on the concave side (<i>p</i> = 0.013). The asymmetry degree of SIJD between the concave side and the convex side was significantly associated with Cobb angle (<i>r</i> = 0.251, <i>p</i> = 0.012) and lumbosacral coronal angle (<i>r</i> = 0.426, <i>p</i> = 0.001). Multivariate regression analysis showed that factors associated with SIJ degeneration were the PIA (coefficient B = 0.153), and LSLA (coefficient B=-0.118). SIJ degeneration was significantly correlated with preoperative VAS-BP, SRS-22 pain, SRS-22 activity and SF-36 PCS (all <i>p</i> &lt; 0.05).</p> Conclusion <p>SIJ degeneration was more severe on the convex side compared to the concave side in DLS, and the asymmetry degree increased with both the Cobb angle and the lumbosacral coronal angle. PIA and LSLA were significantly associated with SIJ degeneration score. These findings highlight the importance of considering the SIJ during preoperative assessment and surgical planning for DLS, particularly in patients with severe SIJ degeneration, which may contribute to low back pain and functional limitation.</p>