ABSTRACT In this paper, we examine the long-run purchasing power parity (PPP) by testing for a unit root in real exchange rates between the US and 14 emerging economies from 1st January 1990 to 31st December 2018. The main objective of this paper is to investigate the real exchange rate adjustment for these emerging economies using both standards linear and nonlinear of exponential smooth transition autoregressive (ESTAR) model. Specifically, the objective is to estimate the PPP adjustment toward long-run equilibrium. The research also aims to model long-run validity of PPP hypothesis using bivariate vector error correction models which we can do with our data. The speed of adjustment is better captured that way as it a bivariate approach. The results seem to suggest that both linear and nonlinear unit root tests fail to reject the null hypothesis of the exchange rates for these emerging economies. One key policy implementation is that the validity of using PPP to decide the equilibrium exchange rate for these 8 countries. Moreover, our vector error correction model seems to suggest that most of the countries do not support PPP. Keywords unit root test; real exchange rates; panel data; non-stationary; Johansen cointegration test, vector error correction model