Word spellings are often a common linguistic issue among Arabic-speaking learners of English, and English vowels are one of the most difficult to resolve. Therefore, the study presented vowel instruction as an intervention to address this issue by determining its effect on the spelling performance on monosyllables and bi-syllables. Vowel instruction sessions were then offered to 15 university freshman students for two months. Instructional strategies consisted of teaching vowel pronunciation, vowel letter-to-sound relationships, vowel spelling patterns, word-breaking, and providing various spelling opportunities. To measure overall spelling performance, pre-test and post-test on vowel spellings were conducted which revealed a significant increase in the mean scores. This suggests that vowel instruction was facilitative in the improved spelling performance on monosyllabic and bi-syllabic words, with more misspellings in the latter than in the former. The strategies used were generally perceived as beneficial, and it is recommended that including them in language lessons could improve vowel spelling skill and minimize English vowel confusions. Moreover, constant exposure of learners to many English words and more spelling activities are still necessary for better English vowel recognition and whole word spelling.