The study aimed to identify the spelling errors among Balochi and Swahili speaker bilingual students. To achieve this, the researcher prepared an objective and diagnostic test in spelling rules. A group of specialists checked the validity of this test. The reliability was measured by calculating Cronbach alpha. It was 0.93 which means that it is suitable for the purposes of the study. The test was applied on a sample of 177 students in the seventh grade in Muscat governorate. The results of the study showed the bilingual students have some common spelling errors in writing Arabic. The most important errors were in the usage of the imperative and the present tense with deleted final vowels, some punctuation marks, gimnation, hamzat al qata, hamzat al wasel, alalef alfareqa, alalef almaqsura, and alalef alqaema. The study also found that there are no significant differences related to the language variable. On the other hand, there are significant differences in spelling mistakes related to sex as the males made more spelling errors. In these findings, the study provided a set of recommendations, such as: • Organize evening classes for those who are interested whether students or parents to learn spelling rules. • Prepare a booklet for each student that contains a series of training activities on spelling rules. The study also provided a number of suggestions for future studies and research such as: Identify the writing performance difficulties in such as Grammar and Morphology. • Design programs that solve the spelling rules problems starting from grade one