This study examines the idiolectal variations of the Mongondow language among the community in Kombot Village, Pinolosian District. The research problem is framed by the emergence of non-homogeneous individual speech variation phenomena as well as phonemic change processes within the same speech community. The objective of this study is to describe the forms of idiolectal variation from a phonological perspective and to thoroughly identify the various factors that influence them. This study utilizes a sociolinguistic approach through a qualitative descriptive method. Research data were collected using observation techniques, in-depth interviews, voice recordings, and note-taking of the native community’s natural speech. The results indicate that idiolectal variation in the Mongondow language is strongly reflected in phonological aspects. These include differences in voice quality (timbre), pitch dynamics, vowel and consonant phoneme modificationssuch as processes of substitution, deletion (apheresis, syncope, apocope), and sound addition (paragoge) as well as the use of distinctive language styles, including narrative description, alliteration, repetition, and emphatic particles. These individual speech variations are influenced by a complex accumulation of internal and external factors. These factors include the physical condition of the speech organs, psychological traits and speaker personality, the geographical environment and occupational habits of coastal communities, as well as the high intensity of language contact and social interaction with communities from outside the village.