Imaginative composition writing skills (IMW) in Kenyan primary schools strengthen learners’ learning, thinking and reflect on their overall academic performance. However, achieving good composition writing is challenging especially to non-native learners of English because of its complexity and nature. Some factors attributed to learners’ writing difficulties are: the curriculum, the pedagogic approach used and teachers’ lack of ability in writing instruction. These factors are in tandem with the ICW status in Vihiga County where over (70%) of Class 8 learners’ composition score are unsatisfactory, 60 % of teachers are uncomfortable to teach ICW while 75% of learners find it boring. To address these ICW difficulties, this study assessed the process approach out of the three principal writing approaches because it’s seen as the best alternative to product approach and that genre approach is considered a newcomer. The objective of the study was to assess the effectiveness of process approach in developing composition writing. Archer’s theory of reflexivity guided the study which used qualitative exploratory research design and was conducted in Vihiga County. Data collection tools were Lesson Observation and Interview Schedules. Validity and reliability were tested through triangulation and thick description. From Class 6-8, 30 lessons in 10 purposively selected schools were observed and 30 teachers interviewed. Data were analyzed thematically through transcription, coding and identification of themes. The key finding was: ineffective utilisation of the process approach due to teachers’ knowledge gaps on the approach. The study recommended teachers to use process approach effectively in ICW and the Ministry of Education to in-service teachers on writing approaches.