Objective <p>This study sought to investigate clinical characteristics of acute anterior ST-segment elevation myocardial infarction (STEMI) patients complicated by new complete right bundle branch block (CRBBB) and evaluate the occurrence of microcirculatory dysfunction post-percutaneous coronary intervention (PCI).</p> Methods <p>Retrospective analysis was conducted on 261 patients with acute anterior STEMI, differentiating 40 with concurrent new CRBBB (CRBBB group) from 221 without (no-CRBBB group). Data on demographics and hospitalization were collected, and clinical features and prognoses were compared. Post-PCI microcirculatory function was further characterized using coronary angiography-derived index of microcirculatory resistance (caIMR), thrombolysis in myocardial infarction (TIMI) grade flow, corrected TIMI flow frame count (CTFC) of the infarct-related artery, and ST segment regression in electrocardiograph (STR).</p> Results <p>Age, Killip class, GLUC, TG, HDL, BUN, GFR, AST, ALT, WBC, TNI at admission significantly differed between groups (<i>P</i> &lt; 0.05). Incidences of in-hospital major adverse cardiovascular events and LVEF showed significant disparities (<i>P</i> &lt; 0.05). The CRBBB group exhibited higher CaIMR, lower TIMI flow, and STR (<i>P</i> &lt; 0.05). Multivariate analysis indicated TIMI ≤ grade 2 (OR = 6.833, 95% CI: 1.009 ~ 46.287, <i>P</i> = 0.049), STR ≥ 50% (OR = 0.176, 95% CI: 0.051 ~ 0.606, <i>P</i> = 0.006), CTFC (OR = 1.079, 95% CI: 1.009 ~ 1.155, <i>P</i> = 0.027), and caIMR (OR = 1.120, 95% CI: 1.059 ~ 1.185, <i>P</i> &lt; 0.001) were independently linked to new onset of CRBBB. Complicated of new CRBBB was strongly associated with elevated CaIMR in anterior STEMI patients. (OR = 5.065, 95% CI:1.793–14.308, <i>P</i> = 0.002).</p> Conclusion <p>In patients with acute anterior STEMI, those with new CRBBB are at an increased likelihood of experiencing microcirculatory dysfunction.</p>