Balloon uncrossable lesions are defined as lesions that cannot be crossed with a balloon after successful guidewire crossing. We analyzed the association between balloon uncrossable lesions and procedural outcomes of 8671 chronic total occlusions (CTOs) percutaneous coronary interventions (PCIs) performed between 2012 and 2022 at 41 centers. The prevalence of balloon uncrossable lesions was 9.2%. The mean patient age was 64.2 ± 10 years and 80% were men. Patients with balloon uncrossable lesions were older (67.3 ± 9 vs. 63.9 ± 10, < 0.001) and more likely to have prior coronary artery bypass graft surgery (40% vs. 25%, < 0.001) and diabetes mellitus (50% vs. 42%, < 0.001) compared with patients who had balloon crossable lesions. In-stent restenosis (23% vs. 16%. < 0.001), moderate/severe calcification (68% vs. 40%, < 0.001), and moderate/severe proximal vessel tortuosity (36% vs. 25%, < 0.001) were more common in balloon uncrossable lesions. Procedure time (132 (90, 197) vs. 109 (71, 160) min, < 0.001) was longer and the air kerma radiation dose (2.55 (1.41, 4.23) vs. 1.97 (1.10, 3.40) min, < 0.001) was higher in balloon uncrossable lesions, while these lesions displayed lower technical (91% vs. 99%, < 0.001) and procedural (88% vs. 96%, < 0.001) success rates and higher major adverse cardiac event (MACE) rates (3.14% vs. 1.49%, < 0.001). Several techniques were required for balloon uncrossable lesions. In a contemporary, multicenter registry, 9.2% of the successfully crossed CTOs were initially balloon uncrossable. Balloon uncrossable lesions exhibited lower technical and procedural success rates and a higher risk of complications compared with balloon crossable lesions.