Objectives The aim of this study was to assess whether ultrasound attenuation and plaque rupture as detected by intravascular ultrasound (IVUS) are associated with the incidence of no-reflow phenomenon after percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI). Background No-reflow phenomenon is associated with worse long-term outcomes after STEMI. Therefore, reliable and feasible intravascular imaging techniques are needed to identify patient subgroups that would be at high risk for no-reflow phenomenon. Methods One hundred seventy consecutive patients with STEMI who underwent PCI within 12 h after symptom onset were enrolled. The IVUS interrogation was performed before PCI. Results No-reflow phenomenon occurred in 30 patients (18%), who had a higher incidence of no ST-segment resolution (50% vs. 9%; p < 0.001), a higher peak creatine kinase level (4,090 IU/l vs. 2,823 IU/l; p < 0.001), and a lower left ventricular ejection fraction in the chronic phase (51% vs. 59%; p < 0.01). Multivariate logistic regression analysis revealed that ultrasound attenuation with a longitudinal length of ≥5 mm, plaque rupture, and reperfusion time correlated with no-reflow phenomenon (all p < 0.05). In patients with both ultrasound attenuation ≥5 mm and plaque rupture, the incidence of no-reflow phenomenon was 88%, and the risk of decreased coronary reflow was higher than that predicted by either factor alone (p = 0.004 for interaction). Conclusions In patients with STEMI, a longer ultrasound attenuation and plaque rupture on IVUS are associated with an increased incidence of no-reflow phenomenon, suggesting that this subset of patients might be at high risk for distal embolism.