The authors examined the effects of captions on deaf students' content comprehension, cognitive load, and motivation in online learning. The participants in the study were 62 deaf adult students who had limited reading comprehension skills and used sign language as a first language. Participants were randomly assigned to either the control group or the experimental group. The independent variable was the presence of captions, and the dependent variables were content comprehension, cognitive load, and motivation. The study applied a posttest-only control group design. The results of the experiment indicated a significant difference (t = -2.16, p < .05) in content comprehension but no statistically significant difference in cognitive load and motivation between the two groups. These results led to suggestions for improvements in learning materials for deaf individuals.