This research analyzed program presentation styles in radio stations and its effects on Kiswahili in Kenya. Radio stations have an important role in the preparation and presentation of programs that inform, educate and entertain their audiences. Different styles of program presentation have continued to be used by radio stations with the aim of attracting audience for profits. This can have adverse effects on language. Kiswahili is one of the languages used for broadcasting in the radio stations thus it stands to develop or not. It is against this background that this research aimed at investigating styles of program presentation in radio stations and its effect on Kiswahili language in Kenya. Specific objectives were; to determine if program presentation styles of sheng' and code switching attract listeners of Citizen Radio, Maisha Redio and Kenya Broadcasting Corporation Radio, to analyse the context where program presentation stylistics of sheng' and code switching are used and how in Citizen Radio, Maisha Redio and KBC Redio and to determine the effects of program presentation styles to Kiswahili language. This study was guided by two theoris; Uses and Gratifications Theory as propounded by Kartz (1974) and later developed by Blumler and Michael Gurevitch and Register Analysis theory propounded by Halliday (1978). The two theoris were used because they explain the reasons as to why people choose and use the mass media and that language use depends on the context of use. The study employed the descriptive research design. Data for this study was collected from Nyoera sub location, Nyamache Sub County in the larger Kisii County and from three radio stations. A sample of 68 respondents who are listeners of the three radio stations under study were used in the research. The respondents were selected using snow ball sampling. Data was collected using questionnaire, listening and recording of selected transmitted programs. Data was analyzed qualitatively by use of explanations and presented using tables. The findings of this study revealed that redio listeners were lured by program presentation stylistics used by radio stations. In addition the program presentation stylistics were used for emphasis, association, as a sign of mastering many languages and ease communication. It was also found that sheng' and code switching have adverse effects on Kiswahili language. This study is significant because it is a call on the radio stations that they have a role to play in developing language through the use of program presentation stylistics.