Background: Acute ischemic stroke (AIS) patients undergoing complex treatments are highly vulnerable to readmission. Limited studies have been performed to compare the 30-day readmission rates and causes in AIS patients treated with Intravenous tissue plasminogen activator (IV-tPA), mechanical thrombectomy (MT), and both. Methods: We obtained national readmission dataset (NRD 2014), a subset of Healthcare Cost and Utilization Project (HCUP) to analyze the 30-day readmission estimates from January to November 2014 after excluding elective readmission. The AIS patients undergoing IV-tPA and MT were identified by using ICD-9 diagnosis codes 99.10, V45.88 and 39.74 respectively. We used SAS 9.4 version for data analysis and SURVEYMEANS procedure was used to measure readmission rate. Discharge weights were provided by HCUP applied to produce national estimates. Results: The NRD contained 341621 admissions (weighted N =741129) of AIS patients in 2014. After excluding elective readmissions, all cause 30-day readmission rate was 10.64%, 13.07%, and 10.66% for IV-tPA, MT and combined treatment group. The top causes of unplanned readmission in all 3 groups were infections and acute cerebrovascular disease. The next common causes for readmission were congestive heart failure, acute renal failure in MT group, transient cerebral ischemia and congestive heart failure in IV- tPA group whereas, cardiac dysrhythmia and complications of medical and surgical care in combined group. Other causes are shown in Table 1 . Conclusions: Infections and acute CVD were the most common culprits of readmissions in all 3 groups. Amidst the ongoing debate over advantage of adding IV-tPA in stroke patients undergoing MT, the insights into 30-day readmission rates and causes comparison will help to strategize post-AIS preventive care to lower down the readmission rates and health care burden.