This paper embarks on the influence of code switching and code mixing in the teaching and learning process in adult learning centers. This paper opted for code switching and mixing since they are well-known traits in the speech pattern of the average bilingual and multilingual in any society in Tanzania. Thus this study attempts to analyze the influence of code switching and code mixing in the teaching and learning process using the Development Interdependence Hypothesis propounded by Cummis (1978) specifically analyzing the influence and reasons why code switching and mixing in the teaching and learning process. Data collection included interviews where students and facilitators were interviewed as well and observations were conducted during ongoing classroom activities such as teaching, seminar presentation and discussions. The recommendation and suggestions on the impact of code switching and mixing have been conducted to give an overall description of this phenomenon.