The J-chronic total occlusion(CTO) channel score can predict guidewire tracking of the collateral channels(CCs), but its efficacy in predicting microcatheter tracking has never been tested in the setting of retrograde CTO-percutaneous coronary intervention(PCI). Predicting microcatheter collateral tracking during retrograde CTO-PCIs. A total of 189 patients undergoing retrograde CTO-PCI from April 2017 to August 2021 were screened. The primary outcome of interest was a correlation between J-CTO channel score and microcatheter tracking failure (MTF) after successful CC tracking by the guidewire. The independent association between anatomical features of the J-CTO channel score and the primary outcome of interest was explored. After adjustment, only small size (adjusted OR: 12.70, 95% confidence interval [CI]: 1.79-89.82; p = 0.01) and continuous bends (adjusted OR: 14.15, 95% CI: 2.77-72.34; p < 0.001) remained significantly associated with an increased risk of MTF for septal collaterals. The small size was the only predictor of the MTF for epicardial collaterals (OR: 6.39, 95% CI: 1.13-35.96; p = 0.020) at univariate analysis. Patients in the MTF group had a lower incidence of procedural success compared with patients in the microcatheter tracking success (MTS) group (40.0% vs. 93.9%, p < 0.001) and had a higher incidence of collateral perforations (20.0% vs. 3.0%, p < 0.001). Small and tortuous septal collaterals, identified by a score ≥3, are associated with an increased risk of MTF, lower incidence of procedural success, and higher risk of procedural complications driven by collateral perforations.