The main purpose of this study is to analyze spelling and grammar error of Afan Oromo modulesrnprepared in Haramaya University. The study identifies the types and causes of spelling andrngrammar errors which are found in the modules. It also focuses on the impacts of the errors on thernstudents and means of minimizing the causes of the errors.rnThree data gathering tools were utilized for this purpose: text analysis, questionnaire andrninterview. Text analysis was used to identify and classify spelling and grammar errors in thernmodules. Questionnaires and interviews were employed to gather data from the respondents. Bothrnqualitative and quantitative methods of data analysis were used to analyse data obtained throughrnthese tools. Questionnaire was used to collect information from third year section â€˜Aâ€™ Afan Oromornstudents. The selection of this section was random. Moreover, nine Afan Oromo teachers wererninterviewed.rnThe finding of the study depicts the existence of spelling errors such as omission, addition,rnanalogy, substitution, transposition, spacing, inconsistency and unclassifiable error types.rnCorrespondingly, grammar errors such as incorrect use of connectives, case markers, parallelrnconstructions, agreements, prepositions and tenses were identified. The use of fragmented sentencernwas also identified. The findings also reveal that these errors affect students' understanding inrndifferent ways. Moreover, carelessness and lack of knowledge which results from absence ofrnpractice, good Afan Oromo academic background and sufficient experience were found to be therncauses of the errors in the modules.rnThus, the researcher recommends revision of the modules, training teachers involved in modulesrnpreparation, giving adequate time for module preparation and preparation of the modules byrnexperienced teachers.