This paper examines the monetary policy rules for five emerging ASEAN economies—Indonesia, the Philippines, and Thailand as the adopters of inflation targeting (IT) and Malaysia and Vietnam as the non-IT adopters. For the methodology, this study applies a generalized method of moments that provides a consistent and efficient estimator for the estimation that contains endogenously determined variables. The questions are whether the rules of the IT adopters have fulfilled the Taylor principle and what has been the difference in the rules between the IT adopters and the non-IT adopters. The main findings are as follows: Regarding the IT adopters, their rules are characterized by inflation-responsive rules fulfilling the Taylor principle. As for the non-IT adopters, Malaysia follows solely an output-gap responsive rule, and Vietnam exhibits the mixed rules. The policy implications are that for the IT adopters there might be room to make their policy-rate responses more elastic to inflation, and that for the non-IT adopters, there would be a need to adopt an explicit IT framework.