Introduction: Early readmission within 30 days (30DR) after percutaneous coronary intervention (PCI) is thought to contribute towards greater healthcare costs. However, no study has examined the exact cost of 30 day readmission after PCI from a hospital’s perspective. Methods: We used the national State Inpatient Databases (SID) which is a part of the Healthcare Cost and Utilization Project (HCUP) from 8 states with long term follow-up to identify the hospital costs through 30 days after PCI. Cost from the hospitals’ perspectives was obtained using published hospital-specific cost to charge ratios. Costs were trimmed to exclude extreme outliers and inflated to 2014 US dollars using the medical consumer price index. Costs through 30 days after index PCI were compared among those who were and were not readmitted within 30 days. A multivariable linear regression cost model was developed to identify the incremental and independent costs of 30DR when adjusted for baseline socio-demographics, clinical characteristics and comorbidities. Results: Of the 539,045 patients undergoing PCI included in the SID from 8 states, readmission within 30 days occurred in 14.7%. Costs of hospitalization through 30 days of index PCI were higher for those readmitted within 30 days ($40,869) vs. those not readmitted ($21,983), P<0.001. These higher costs were contributed by a higher index PCI hospitalization costs of $25,943 for patients readmitted within 30 days vs. $21,983 for those not readmitted, P<0.001 as well as costs of subsequent readmission hospitalization within 30 days ($14,926). When adjusted for baseline socio-demographics, clinical characteristics and comorbidities, 30DR incrementally cost $1,384 (95% CI $1,254 to $1,513, P<0.001). Conclusions: This study, to the best of our knowledge, is the first study to examine the cost of early readmission within 30 days of PCI. Readmissions within 30 days of PCI are expensive and contribute towards excessive healthcare costs. This study further supports systematic efforts to reduce 30DR after PCI.