Dissertation (MA Education)The purpose of this study was to investigate effects of large class size on effective teaching and learning process in public primary schools in Tanzania: The study was guided by the following objectives: to explore pupils, teachers, WECs and MEO conceptions of large class size, to identify challenges that faced teachers and pupils in large classes in primary schools and eventually suggest possible strategies for addressing challenges posed by large class size in public primary schools. The study employed a case study research design, where 165 respondents were involved. The sample included 100 pupils, 50 teachers, 10 head teachers, 4 Ward Educational Coordinators and 1 Municipal Educational Officer. Simple random and purposive sampling was used in the study. Data were collected through questionnaires, interviews, observations and documentary reviews. The collected data were analysed by content analysis and statistical package for social sciences (SPSS) Version 20.0. The study revealed that 43 (66.1%) of respondents conceived large class size as a class that limit teachers use of interactive teaching methods. The study also revealed a range of challenges that faced teachers and pupils pertinent to large classes included; difficulty in classroom management, difficulty in classroom assessments and difficulty in marking pupils’ exercises. The study revealed also the effects of large class size on teaching and learning process including; large class size limits pupil-pupil and teacher-pupil interactions and it lower pupils’ academic performances.M ain strategies for addressing challenges posed by large class size included applying interactive teaching techniques, team teaching and the use of double shifts. The recommendations of this study were such that the government had to build new schools and/or classrooms, employ many teachers and provide enough pupils’ desks as well as teaching and learning materials.