This study explored perspectives on using Swahili in English language classes and describe how teachers utilise this language in English language classes. It was a qualitative approach. Data were collected through focus group discussions, interviews, and classroom observations. In all, six secondary school teachers and three classes drawn from six secondary schools participated in the study. Findings show that even though using Swahili fostered the learning of concepts, it was inappropriate for developing English-speaking proficiency. It emerged that using Swahili in teaching the English language exposes language and pedagogical deficiencies in Tanzania's classes. Moreover, the persistent use of Swahili in English language classes was attributable to the learners' lack of confidence in speaking English. As a result, English language teachers adopted Swahili as a teaching strategy in addition to directing students to accomplish classroom tasks and expressing their emotions in that language. Thus, there is a need to review Tanzania's education policy need to accommodate the use of Swahili in English language classes as part of a translanguage setup while exploring means for fostering ESL speaking skills particularly among students.