Studies have established that adequacy of instructional resources spices the learning environment and therefore contributes immensely to the effectiveness of the teachers in the learning process. In Nyakach Sub-County, concerns have been raised on the effectiveness of teachers with regard to the adequacy of instructional resources in use during the learning process. This article therefore, purposed to establish the relationship between the adequacy of instructional resources and effectiveness of teachers of Literature during their lessons. The study is conceptualized on the effect of the interaction between Independent Variable (Instructional resources-adequacy of instructional resources) and Dependent Variable (Teacher effectiveness). Correlational and descriptive survey designs were adopted; target population was 140 high school teachers teaching Literature while the sample was 42 teachers of Literature. Systematic random sampling and purposive sampling techniques was used to select Teachers. Data collection instruments were Classroom Observation Guide (COG) and Teacher Questionnaire (TQ). Reliability was established by piloting 10% of the population using test-retest method. Chronbach‟s alpha was used to determine instruments’ reliability with COG and TQ coefficients being 0.833 and0.797 respectively thus considered reliable. Face and content validity were ascertained by experts. Analysis was done through descriptive and inferential statistics. These were by means, standard deviations and multiple regressions. Findings indicated that level of adequacy was not significant at (r=-0.038, p-value=0.497>0.05) with regard to teacher effectiveness. The study concludes that instructional resources were inadequate and level of adequacy of instructional resources was not statistically significant. These findings may be useful to principals, teachers and curriculum developers in making informed decision with regard to adequacy in the provision of instructional resources in secondary schools.