Kikuyu language is a highly agglutinative language with an S-V-O sentence structure. This study aims to find out the phonological processes of the Kikuyu dialectical words and determine the phonological rules. A limited number of studies have been done in the Kikuyu language concerning the phonological processes. Therefore, this study is justifiable because it will not only give more lexical units which are subject to phonological processes in the Kikuyu language, which may be inadequate in the previous studies but also create awareness among the scholars of the various Kikuyu lexicons which undergo the phonological processes. The data for analysis is presented using phonetic transcription, and it was collected from the native, resourceful speakers of the Kikuyu language and from selected Kikuyu texts like Phonetics and Tonal Systems of Kikuyu (Lilias Armstrong, 2017) and Modern Gikuyu Dictionary: Gikuyu-English, English-Gikuyu (Kasahorow, 2014). The Distinctive Features theory is used in the phonological analysis of the data. The results of the study showed that different Kikuyu words undergo phonological processes evident in this study, like assimilation, consonant strengthening, glide formation, nasal coalescence, consonant coalescence, insertion, and vowel deletion.