The goal of the study was to examine effect of Tax aggressive strategy on internal efficiency and customer loyalty of listed manufacturing firms in Nigeria for the period 2004 t0 2023 using secondary data obtained from firm’s financial statements. Tax aggressiveness was measured using allowable expenses for tax purposes, debt and non-debt tax shield and internal efficiency and customer loyalty as dependent variables. Hausman test for selection of model, multiple regression and panel corrected standard error for determination of relationship. Various classic assumption tests were conducted on data set to ascertain reliability and ensure appropriateness of result. Result of the study confirmed all tax shield variables exert significant impacts on internal efficiency of manufacturing companies in Nigeria. It was however found that while allowable expenses tax shield and debt tax shield had significant negative effect, the effect of non-debt tax shield is positive. This also demonstrates a mutually exclusive relationship in this regard. Further Corporate tax shield variables all have significant effects on customer loyalty of manufacturing companies in Nigeria, although the effects are mutually exclusive. While that of allowable expenses tax shield is negative, debt and non-debt tax shields exert positive effects on customer loyalty. Based on outcome, it is recommended that corporate tax strategies should be considered as a strategic adaptation rather than a deliberate manipulation strategy of management in order to drive long term performance, especially in relation to the market performance of firms. There is the need for manufacturing firms to improve non-debt tax shield in order to improve their positions before customers. Results reveal that customer loyalty favors firms with non-debt tax shield tax aggressiveness.