This study aims to conduct a comparative analysis of the impact of informational transparency on the depth of the Islamic debt securities markets in Iran and Malaysia over the period 2010–2024. Given the growing importance of transparency as a fundamental pillar of financial market efficiency, the research investigates how institutional frameworks, disclosure quality, and regulatory structures explain differences in the depth of Islamic debt markets across the two countries. Key transparency indicators — including financial disclosure practices, credit rating requirements, regulatory independence, and digital reporting infrastructure — are first compared. Then, using a linear regression model and macro-institutional data from 2010 to 2024, the relationship between market depth and economic growth, inflation, interest rates, and transparency is estimated for both countries. The findings indicate that informational transparency and economic growth have a positive and statistically significant effect on market depth, while inflation and interest rates exhibit a negative but statistically insignificant impact. Moreover, the effect of transparency is notably stronger in Malaysia than in Iran. These results support the main hypothesis of the study and suggest that enhancing regulatory institutions, improving disclosure mechanisms, and strengthening information infrastructure in Iran could be crucial steps toward deepening its Islamic debt market.