Background: Adjunctive balloon post-dilation (ABP) using compliant stent delivery balloon in the proximal area comprising angiographically normal native coronary artery segment to the underexpanded proximal portion of the implanted stent may be a cost-effective strategy compared with traditional ABP using new larger non-compliant short balloon. We investigated whether there are acute procedural complications such as intimal dissection or thrombosis and subsequent adverse clinical outcomes due to the balloon injury up to 6 months. Methods: A total 71 out of 1126 patients (6.3%) who underwent percutaneous coronary intervention (PCI) with drug-eluting stents (DES) showed stent underexpansion received ABP with higher pressure than nominal pressure using stent delivery balloon for further stent expansion. We compared the in-hospital and 6-month clinical outcomes of the proximal balloon group to those of no proximal balloon group. Results: Baseline clinical and procedural characteristics were similar between the two groups. There were no significant differences in acute procedure-related complications and in-hospital clinical outcomes between the two groups. We failed to find the any differences in terms of adverse short-term and mid-term clinical outcomes between Proximal Balloon group and No Proximal Balloon group (total MACEs 2.6% vs. 2.8%, p=0.71). Conclusions: ABP using stent delivery balloon in the proximal area comprising angiographically normal native coronary artery segment to the underexpanded proximal portion of the implanted stent can be a cost-effective strategy in selective patients.