Subject- verb agreement is very basic knowledge in making an English sentence. To produce a complete sentence, the students at least have to put one subject and one verb, and here is the importance of subject-verb agreement. This research aims at knowing the error types and calculating the production of subject-verb agreement error in students’ writing. However, the researcher limits the subjectverb agreement sentences on seven subjects, namely I, we, you, they, she, he, and it and later called as keywords. The data were collected from 99 essays from International Relations essay writing class batch 2016 at Language Training Center of Universitas Muhammadiyah Yogyakarta. In this research, the researcher used error analysis as design of this research, based on Corder (1967) in Agustina (2016) that was determining the data, identifying the errors, classifying the errors, explaining the error and quantifying the error. The researcher used document analysis as data collections method and Concordance program as help for shorting the data. The results of this research showed that there were 363 subject-verb error sentences from 2,851 sentences which contained seven keywords. There were four types of errors on International Relation essay writing class batch 2016 when used subject-verb agreement in their writing. They were addition, misformation, misordering and omission (Ellis, 2003). However, not all of seven keywords had all of four error types. Keywords “I”, “We”, “You”,“They”, “She”, and “It” had all of errors type, but for keywords “He” only had three error types, which were misformation, misordering, and omission. From those errors, the types of error that occurred mostly was misformation (43.80 %), the second was omissions (38.90%), the third was additions (10.00 %), and the last misorderings (7.50%). Finally, the total subject-verb agreement error percentage was14.19 % meaning that the error level was low.