This study aimed at: a) analyzing the types of code-mixing used by Indonesian top selebgram in social media in product endorsement; b) analyzing the reasons of code-mixing used by Indonesian top selebgram on her captions in product endorsement; c) analyzing the language used by the Indonesian top selebgram in product endorsement through her captions on Instagram. The sample of this study was a female selebgram namely Karin Novilda or well-known as @awkarin. The subject was chosen through purposive sampling who tend to use code-mixing within her posts in promoting product endorsement. The data were gathered through observation check-list which consisted of Instagram post including picture, date of posting, and captions from March to August 2021. The results indicated that, first, the most dominant type of code-mixing used was insertion; second, the most dominant reasons of the use of code-mixing was talking about particular topic; and third, directive speech acts appeared dominantly as the characteristics of the language in form of command, suggestion, invitation and also feeling expression of the subject. These findings have important contribution to see how the use of code-mixing assisted the Indonesian top selebgram in doing product promotion.