Teacher professional development encompasses the process of improving the skills, knowledge and competencies of classroom teachers with an intention to make the teachers more efficient and improve their teaching practices hence achievement of desired outcomes for students. This study determined the influence of teacher’s professional development on the implementation of language activities in competency based curriculum in public primary schools in Homa bay County, Kenya. The study adopted descriptive survey research design. The target population consisted 1119 teachers. Stratified sampling was used to divide teachers into grades they teach, simple random sampling was applied to select teachers from each strata. The Sample size of the study was 223 which was 20.0% of the target population. Questionnaires were used on teachers while observation checklist was used on schools. 4 primary schools were used to pilot in Kasipul sub –county, where 8 teachers participated. Qualitative data were analyzed thematically and presented in narrative form. Quantitative data were coded and analyzed using SPSS version 27 to generate frequencies and percentages. Inferential data analysis was done using linear regression to determine the influence of teacher professional development on implementation of language activities. The study found that teacher professional development had a 63.1% variation to explain and predict implementation of language activities while majority of teachers were not satisfied with the preparedness level to implement the curriculum. The findings of the study may inform the education stakeholders such as the Ministry of Education to come up with content training programs and policies that assist in curriculum implementation.