This article is part of a larger study conducted to assess levels of Mother tongue proficiency among primary school pupils in Meru Central District, Kenya. The study focused on assessment of the levels of Kimeru proficiency among lower primary 0school pupils and its impact on literacy among early learners. The study was conducted in five primary schools in Meru Central District using a descriptive research design. The target population comprised of thirty standard four pupils from three public primary schools and twenty teachers from both public and private schools while the research instruments were Kimeru proficiency tests and focused group discussions. This research only focused on class four pupils in selected public primary schools for the reason that they had just stopped learning Kimeru at school. Data was analyzed using quantitative and qualitative methods. The study found out that there are low levels of Kimeru proficiency among primary school pupils. Cognizant of the role Mother tongue proficiency plays in early literacy and learning; primary school pupils have a difficult task acquiring literacy and accessing curriculum (which is in English).