This study investigated the influence of cartoon viewing on English language proficiency among children aged 4 to 8 years in Nairobi City County. Recognizing the importance of English as the official language and medium of instruction in Kenyan educational institutions, this research addressed the challenges of English language acquisition in a culturally and linguistically diverse environment. Using an experimental research design, the study evaluated the impact of cartoon viewership on speech proficiency, focusing on four key components: watching and listening to cartoons, cartoon imitation, preference for specific cartoon programs, and cartoon viewership patterns. The target population comprised both public and private primary schools, reflecting Nairobi's varied socio-economic landscape. Participants were divided into experimental and control groups, with pre-test and post-test assessments conducted to measure changes in speech proficiency. Additionally, in-depth interviews with teachers of Grades 1 to 4 provided qualitative insights. Quantitative data were analyzed using paired t-tests, while qualitative data underwent content analysis. The study found that cartoons significantly enhance speech proficiency in children when integrated with active participation like singing, drawing, and role play. Imitating cartoon characters' speech and gestures improved vocabulary, sentence structure, and expressive communication. Children’s preferences, such as genre, language, and character type, also influenced speech development, with dialogue-rich, English-language cartoons proving most effective. In addition, viewing patterns like time of day, frequency, and duration impacted outcomes, with consistent, structured exposure yielding better results. The study recommends that practitioners use cartoons intentionally to enhance speech development in children by encouraging active engagement and imitation of characters’ speech and gestures. Educators should integrate dialogue-rich, age-appropriate content into lessons and tailor it to children’s preferences. Viewing should be structured, preferably in the morning, and should exceed one hour to ensure effective learning. Policymakers are urged to embed cartoon-based learning in early education frameworks aligned with the Competency-Based Curriculum. Communities and caregivers should support educational cartoon viewership at home and in communal settings, fostering shared learning and reinforcing communication skills beyond the classroom.