This research focused on an assessment on the impact of Kiswahili language structure in teaching and learning English language structure in secondary schools in Ilemela district in Mwanza Region. The study was guided by the following specific objectives: 1. To determine the relationship between Kiswahili language structure and English language structure. 2. To assess the extent to which Kiswahili language structure influences teaching of English language structure in secondary schools. 3. To assess the impact of Kiswahili language structure on the part of secondary school student in learning English language structure. In this study qualitative techniques were used to analyze and manage the data that were collected. The study results or findings revealed Kiswahili language structure have both similar and different forms of relationship with English language structure at different levels of language such as phonologically, morphologically, semantically, syntactically and contextually. These result to either negative or positive impacts or transfers of learning English language structure in secondary school learners.