The research aims to analyze the impact of cross border acquisition on post-acquisition performance of the acquirer's and whether the impact is different when target firm has high level of investor protection or high level of IFRS adoption compared to target firm acquisition with low level of investor protection or low level of IFRS adoption. This study uses 510 companies listed in Asia region that performs acquisition in 2012-2013 as a sample. This study uses several measurement of performance which is return on asset, earnings per share growth, and revenue per share growth. These results indicate that cross border acquisition has a positive impact on post-acquisition performance of the acquirer’s except for return on asset that measures efficiency of asset utilization. Investor protection and IFRS adoption level weakens the impact of cross border acquisition on post-acquisition performance of the acquirer’s. These results indicate that high level of investor protection in target firm require acquirer to comply with strict regulation and lower flexibility to implement their business strategy. While the weaken effect of IFRS adoption on the impact of cross border acquisition on post-acquisition performance implies that acquirer needs time and a high cost to adopt IFRS.