The success of the ERP system implementation has a great importance in Egyptian companies. This research seeks to know the relationship between the success factors of the ERP system (strategic, tactical, and technological) and support decisions in mobile telecommunication companies in Egypt (Vodafone, Orange, Etisalat, WE). Data were collected through a survey list distributed to 443 respondents from the top and middle management mobile telecommunication companies in Egypt. The results indicate that there is a significant impact of the success factors of the ERP system on supporting the decisions of upper and middle management in mobile telecommunication companies. Also, differences were found in the level of perception of upper management and middle management of success factors according to their different demographic characteristics (years of experience, education level).