Purpose: The study aims to evaluate the readability, comprehensibility, and vocabulary knowledge of SRH educational materials available online and on paper to inform health educational material development for young adolescents. Design/methodology/approach: The study used a sequential mixed-method design. Thirty-four online and one print adolescent sexual and reproductive health educational materials were assessed for readability. Two hundred and sixty-three adolescents aged 11-15 participated in the comprehension and vocabulary knowledge assessment of the online sexual and reproductive health texts. Comprehensibility was measured using a cloze test, and vocabulary knowledge was assessed based on a vocabulary knowledge passage. Data processing was performed using SPSS, version 26.0 and the online readability consensus calculator, version 1.0. We analyzed the data using readability algorithms, cross-tabulation and bar charts. Findings: The results show higher readability levels for online SRH materials. Average Flesch reading ease scores range between 37.5% and 69.1%. Other average range indices were the Flesch Reading Grade Level (7-14), Gunning Fog Index (8.8-19), Simple Measure of Gobbledygook (6.6-10.6) and Common-Lieu Index (7.5-11.5). Nearly 51% of participants in the comprehension assessment read at the instructional level. The Chi-square test for grade level differences shows a statistically significant (X2 = 11.349; p = 0.003) difference in comprehension between 7th and 8th graders. The participants also identified 29 words from the 1,048-word passage for assessing vocabulary knowledge as unfamiliar and difficult, and 14 as familiar but difficult to understand. Originality/value: The study's findings may inform the design of health educational materials and provide a basis for a national decision on the readability threshold of adolescent health information.