Abstract: The purpose of this study was to investigate the effect of teachers’ morale on standard eight pupils’ academic achievement in public primary schools in Marani Sub-County, Kenya. The study utilized ex-post facto design. The target population was 320 standard eight teachers in 64 public primary schools. Simple random sampling technique was used to select teachers. The sample size was 100 teachers which represented 30% of the population. Questionnaire was used as data collection instrument. A standardized mock examination mean scores of standard eight pupils was obtained from the Sub-County education office. Data was analyzed using both descriptive (frequencies, percentages and means) and inferential statistics (Pearson coefficient of correlation). All null hypotheses tested at 0.05 alpha level were rejected and led to affirmation that there was a significant relationship between teachers’ morale and pupils’ academic achievement. Based on the results, it was recommended that teachers should be encouraged to prepare teaching-learning instruments, participate in internal quality assurance programmes and attend classes regularly. Teachers should also be motivated and supported by educational stakeholders for better academic achievement in schools.