Objectives To evaluate the diagnostic performance of zero echo time (ZTE) MRI in the depiction of structural lesions of sacroiliac joints (SIJs) in patients with the suspicion of sacroiliitis compared with T1-weighted fast spin echo (T1 FSE), using CT as the reference standard. Methods Forty patients with suspicion of sacroiliitis underwent both CT and MR scans of SIJs with 80 SIJs (160 bone articular surfaces) included for analysis. Two readers independently scored SIJs for structural lesions on CT and MR images. The diagnostic capability of ZTE MRI and T1 FSE were compared by the McNemar test, using CT as the reference standard. Agreements of diagnosis and sum scores of lesions between MR sequences and CT as well as between readers were also investigated using Cohen's kappa appa tests and intraclass correlation coefficients. Results Diagnostic accuracy of ZTE MRI was higher than that of T1 FSE for erosions, sclerosis, and joint space changes (e.g., joint space changes: 91.3% vs 75.0%). ZTE MRI also improved sensitivity for detection of erosions and sclerosis (e.g., erosions at the joint level: 98.2% vs 80.0%) as well as specificity for detection of joint space changes (93.0% vs 67.4%). ZTE MRI had more consistency with CT than T1 FSE for both diagnosis and sum scores. Inter-reader agreements were higher for CT and ZTE MRI than those for T1 FSE. Conclusions ZTE MRI showed superior diagnostic performance in the depiction of SIJ structural lesions compared with routine T1-weighted MRI and had reliability comparable to CT.