This study discusses about the phonological acquisition of mother tongue or first language of a child, 2.6 years old, namely Rasyid Hidayat. The purpose of this study is to describe the forms of phonological acquisition of mother tongue of Rasyid Hidayat by analyzing the phonemes of language that have been mastered. In this study, the researcher uses descriptive qualitative approach which describes and gives understanding about language phenomenon that the researcher want to analyze based on the researcher's point of view. The data collected were gained from recording and note taking. In presenting the data analyzed, the researcher uses formal and informal way. The findings show that the participant has mastered 1) all vowel phonemes such as /a/, /i/, /u/, /e/, and /o/ which have occupied all positions in many words, 2) consonant phonemes such as /p/, /b/, /m/, /n/, /t/, /h/, /s/, /c/, /w/, /y/, /q/, and /k/ where not all of them have already occupied all positions in some words.