The present study examined the effects of orthographic transparency on reading ability of children with dyslexia in two Hebrew scripts. The study explored the reading accuracy and speed of vowelized and unvowelized Hebrew words of fourth-grade children with dyslexia. A comparison was made to typically developing readers of two age groups: a group matched by chronological age and a group of children who are 2 years younger, presumably at the end of the reading acquisition process. An additional purpose was to investigate the role of vowelization in the reading ability of unvowelized script among readers with dyslexia in an attempt to assess whether vowelization plays a mediating role for reading speed of unvowelized scripts. The present study found no significant differences in reading accuracy and speed between vowelized and unvowelized scripts among fourth-grade readers with dyslexia. The reading speed of fourth-graders with dyslexia was similar to typically developing second-graders for both the vowelized and unvowelized words. However, fourth-grade children with dyslexia performed lower than the typically developing second-graders in the reading accuracy of vowelized script. Furthermore, for readers with dyslexia, accuracy in reading "both" vowelized and unvowelized words mediated the reading speed of unvowelized scripts. These results may be a sign that Hebrew-speaking children with dyslexia have severe difficulties that prevent them from developing strategies for more efficient reading.