The study investigated the moderating effect of implementation challenges on ERP adoption and internally generated revenue. The study population consists of the entire six States in the Southwest Nigeria (Lagos, Ogun, Oyo, Osun, Ondo and Ekiti). The study employed annual secondary data from 1999 to 2018. The data were sourced from the National Bureau of Statistics, Budget office and Board of internal revenue of Southwest states. The variables are real average IGR during and post ERP adoption, Pre-ERP adoption performance, and total annual revenue of States. Data collected were analyzed using descriptive and inferential statistical (squared (n2), tow-ANOVA and multiple regression model). Analysis investigate the moderating effect of implementation challenges on ERP adoption and internally generated revenue in Southwest Nigeria revealed that a significant positive linear relationship exists between Internal generated revenue and implementation hurdles (p<0.05; t=0.002) and revenue (p<0.05; t=0.000) in Southwest Nigeria. The study concluded that weak relationship exists between the implementation hurdles and the internally generated revenue, whereas, a strong relationship is observed between cost of ERP adoption and internally generated revenue in Southwest Nigeria which implied that increment in cost of ERP adoption is not necessarily increasing in the same trend as the benefits of ERP adoption.