This study focused on English interference found in Indonesian magazines. Interference is one of bilingualism aspects that occur when a speaker learns a second language. In this case, the interference of English into Indonesian found in the magazines was chosen because most articles in the magazines use English words in their articles which conveyed the occurrence of English interference in Indonesian. This study intended 1) to identify the interference of English in Indonesian magazines, especially identifying the forms of English interference in the Indonesian articles found in Indonesian magazines, namely Tempo and Cosmopolitan Indonesia 2) determine the factors that causing the interference of English in those Indonesian magazines. This study used descriptive qualitative method by applying it to analyze the data, especially the English words and phrases that applied in the Indonesian texts. The units of analysis of this research are English words and phrases used in the Indonesian articles found in Tempo and Cosmopolitan Indonesia magazines. The magazines were chosen because there were many English words found almost in every pages of the magazines. This study becomes interesting because there are many English words can be found in the magazines, but people are often confused whether those words have already adapted as the Indonesian vocabulary or not, besides many people are not familiar with the Indonesian equivalences for many English words that usually applied in the Indonesian text. This circumstance can be either beneficial or harmful to the existence of certain language as well as the ability of the speaker to communicate in a certain language properly. The analysis found that the lexical interference occurred in both magazines. The factors caused the English interference in the Indonesian magazines are the lack of knowledge, bilingualism, lack of vocabularies mastered by the writers, prestige, style, and the synonym needs.