Word formation refers to the act of creating new words and meanings. This research seeks to analyze the types of word formation processes found in Kamus Bahasa Gaul Kaum Milenial and what languages are used during word formation processes. The are the dictionary entries and sampled alphabetically in sequence starting with A, capping the data at 100 total items, which covered the letters A through M. There are two word formation processes in this study, which are multiple word formation processes and single word formation processes. In multiple word formation processes , there are 3 types of multiple word formation processes that happen six times in the book, which are one blending and acronym, one compounding and acronym, and four bdata lending and blending. In single word formation processes, there are three types of single word formation processes that occurred in the book. The writer found that there are 63 blending, 25 acronyms, and 6 clipping. There are more than one languages used in the book. There are Indonesian, English, and local languages, which are Sundanese, Old Sundanese, Betawi, Javanese Palembang, Malay, Jambi Malay, Banjar, and Bahasa Using.