Pronunciation is one of the important things in communication. However, Indonesian students still mispronounced some words in English diphthongs. The purpose of this research is to find out how Indonesian freshmen pronouncing English diphthong. This research used qualitative method and document analysis for the research design. This research was conducted at English Education Department of Universitas Muhammadiyah Yogyakarta. The participants of this research were students of EED of UMY batch 2016 because they were the freshmen at EED of UMY. The researcher took 29 documents of student’s test. The documents were from recording of pronunciation owned by the lecturer of Capita Selecta on Linguistics. Then, the result showed that Indonesian freshmen still mispronounced in each English diphthong. These mispronunciations occurred in each of diphthong [ɪə], [ʊə], [aʊ], [əʊ], [eə], [ͻɪ], [aɪ], and [eɪ]. In this result, diphthong [ɪə] was pronounced as [ɪə], [з:], [ɪ:], [ɪe], [e], [eə], [ӕ], [ə], & [eɪ]. Diphthong [ʊə] was pronounced as [ʊə], [u:], [ɒʊ], [əʊ], [з:], [ɵ], [ͻ:], [ɒ], [ʊ], [ɒə], and [ə]. Diphthong [aʊ] was pronounced as [aʊ], [ɒ], [ᴧɵ], [ɒʊ], [ᴧɒ], [ᴧ], [ᴧʊ]. Diphthong [əʊ] was pronounced as [əʊ], [ɵ], [ɒ], [u:], [ə], [aʊ], [ͻʊ], [əu], [ɒʊ], [ͻ:], and [ᴧ]. Diphthong [eə] was pronounced [eə], [e], [ɑ:], [eɪ], [ə], [з:], [ɪ:], and [ӕ]. Diphthong [ɔɪ] was pronounced as [ɔɪ], [aɪ] and [ɒɪ]. Diphthong [aɪ] was pronounced as [aɪ], [eɪ], [ɪ], and [ᴧe]. Then diphthong [eɪ] was pronounced as [eɪ] and [aɪ].