Pronunciation is one of the determiner aspects in English as it can change the meaning of the words and sentences. This research discusses the analysis of errors in the pronunciation of triphthongs in words and sentences in English. The research was aimed to know the types of triphthongs often mispronounced in the pronunciation of words and sentences in English among second semester students in class A of Speaking for workplace communication lecture at English study program of Madiun State Polytechnic. The quantitative were used after being collected from the assignments and pronunciation tests for several words and sentences containing triphthongs during the research. The research results are described in percentages. The diphthong errors that students often make are //a?? /= 34.6%, /a?? /= 31.8%, /??? /= 20%, /???/= 9%, and /e??/= 4.6%. Errors that occurred in the classification of substitutions = 43.64%, insertions = 32.73%, and omissions = 23.63%. The errors occur due to the influence of inter-language and intra-language factors of the students.