This study is an OT investigation of the morpho-phonology of English loanwords in Kitigania, a dialect of Kiimeru language. The subject of loanwords and adaptation is pivoted on the assumption that Kitigania has had a long time contact with the English language. This English-Kiimeru language contact can be traced back to the coming of missionaries to Kenya in the late 1890’s and the subsequent colonial experience. The study therefore endeavours to: identify English loanwords in Kitigania; investigate the morpho-phonological processes in the adaptation of loanwords; and examine the extent to which the adapted loanwords deviant from the source word. Of significant interest are the phonological and morphological changes that English words undergo in order for them to be accommodated in Kitigania. On account of these, the researcher adopted purposive sampling technique in identifying four social language domains from which speech samples were recorded. Purposive sampling was instrumental in obtaining speech samples rich in loanwords. Further, purposive sampling excluded the possibility of tape recording non-native speakers of Kitigania. The loanwords that were realized from these speech samples were then counterchecked through structured interviews with competent speakers of Kitigania, who were also purposively sampled. The study confirms that Kitigania has borrowed extensively from English. Further, it established that phonological processes such as assimilation, consonant hardening and weakening, deletion, consonant substitution, epenthesis and prefixation of noun class morpheme markers constitute morphophonological processes responsible for the adapted English loanwords in Kitigania. The study notes that English loanwords in Kitigania constitute phonemic loans, and hence the close semblance of the adapted loanwords with the input forms. The OT analysis of the phonological and the morphological processes in the adaptation of English loanwords in Kitigania attests that OT can sufficiently account for the morpho-phonological processes in loanword adaptation in Kitigania. In addition, the findings of the study are beneficial to media practitioners in Kimeru who along their duty, are at times forced to adapt a word on the spot. The study has further enriched linguistic study of Kitigania, a dialect of Kiimeru language.