Code mixing is a sociolinguistic phenomenon that deals with bilingual speakers' ability to use language features of two languages in one sentence or utterance. This research investigated the type of code-mixing used by an Indonesian celebgram and explored reasons for using code-mixing in Instagram captions of an Indonesian celebgram. The data for this study were collected from Instagram captions posted by an Indonesian celebgram @keanuagl from February 2020 to September 2020. The data were analyzed by using Muysken’s theory of type of code-mixing. The reasons for using code-mixing in Instagram captions were analyzed using Hoffman's theory which covers seven reasons. The findings showed that insertion was the most frequent type of code-mixin...