Background In transcatheter aortic valve replacement (TAVR), accurate aortic annulus measurements are essential for prosthesis sizing to ensure procedural success. Although multi-slice computed tomography (MSCT) is considered the gold standard for aortic annulus measurement pre TAVR, MSCT might be contraindicated in some patients. Aim In patients undergoing TAVR, we sought to correlate manual and newer semi-automated three-dimensional (3D) transesophageal echocardiography (TEE) aortic annular measurements to MSCT measurements. In addition, we assessed the reproducibility of these 3D TEE methods. Methods Retrospective, single centre trial involving 39 patients with severe symptomatic aortic stenosis (AS) planned for TAVR, who underwent both pre-procedural MSCT and pre/peri- procedural manual and semi-automated 3D TEE. Results Mean age was 85.3 ± 4.7 years. Both 3D TEE methods highly correlated with MSCT for annular diameters (semi-automated r =0.96, p<0.0001 and manual r=0.84, p<0.0001) and for annular areas (semi-automated r=0.96, p<0.0001 and manual r=0.82, p<0.0001). Inter-observer reproducibility was high for both 3D TEE methods for annular diameters (semi-automated r=0.96, p<0.001 and manual r=0.91, p<0.001) and annular area (semi-automated r=0.96, p<0.0001 and manual was 0.95 p<0.0001). Conclusion Both semi-automated and manual 3D TEE for sizing of the aortic annulus for TAVR is comparable to MSCT. 3D TEE methods are easily reproducible. Newer semi-automated 3D TEE has the best correlation to MSCT. 3D TEE is an excellent alternative imaging modality for TAVR planning in patients whom MSCT is contraindicated.