Introduction Deaf and hard-of-hearing (DHH) students experience persistent difficulties in science education due to language and communication barriers, emphasizing the need for effective visual and multimodal instructional approaches. This study investigated the effects of graphic organizer-supported instruction on the scientific process skills (SPS) of DHH students.Methods A mixed-methods design was employed with 65 DHH students from primary, middle, and high schools and 6 teachers. Graphic organizer-supported activities were integrated into science instruction. Quantitative data were analyzed using repeated-measures ANOVA, while qualitative data were obtained through semi-structured interviews and analyzed using content analysis.Results Findings revealed a statistically significant improvement in SPS across measurement points. Students' positive attitudes toward science significantly influenced performance, whereas grade level showed no significant effect. Observation skills demonstrated the greatest improvement among SPS dimensions. Qualitative findings supported the quantitative results and highlighted the importance of multisensory instruction, repetition, structured visual supports, and vocabulary development.Discussion The findings suggest that graphic organizers are effective in enhancing SPS among DHH students and support the use of visual and multimodal strategies in inclusive science education. Future studies may employ experimental and longitudinal designs to examine long-term effects.