This study aims to find out the types of grammatical errors and analyze the grammatical errors committed by second semester students of English Language Education Study Program at Ganesha University of Education. This study is classified into qualitative research design. To analyze the data, theory types of errors proposed by Dulay et al. (1982) and sources of error from Richards (1974) were applied. The data were sentences on narrative essay writing containing errors taken from final assignments of the second semester students of the English Language Education Study Program at Ganesha University of Education. There are 86 data containing omission, 34 data containing addition, and 286 data containing misformation. Meanwhile, the source of grammatical error that the researchers found are 6 errors caused by interlingual transfer and 22 caused by interlingual transfer.