Unlike English, short vowel sounds in Arabic are represented by diacritics rather than letters. According to the presence and absence of these vowel diacritics, the Arabic script can be considered more or less transparent in comparison with other orthographies. The purpose of this study was to investigate the contribution of working memory to vowelized and non-vowelized reading comprehension and determine whether working memory is more involved in non-vowelized than vowelized reading comprehension. Forty-nine Arabic speaking children from grade six (age 11) undertook two measures of reading comprehension (one vowelized and one non-vowelized). They were also given measures of word reading fluency, vocabulary, phonological awareness, rapid naming and listening span as a measure of working memory. The results indicated that both vowelized and non-vowelized texts were associated with the measure of working memory after controlling for vocabulary, word reading and phonological processing. Although the results are more consistent with common influences of working memory across the two orthographies, slightly larger effects of working memory on non-vowelized reading comprehension suggest that further research, potentially with younger cohorts of Arabic readers would be appropriate. The findings are discussed and future directions for research are suggested.