Open Educational Resources (OER) can offer educators the necessary flexibility for tailoring educational resources to better fit their educational goals. Although the number of OER repositories is growing fast, few studies have been conducted to empirically test the effectiveness of OER integration in the classroom. Furthermore, very little is known about the benefits of utilizing OER in high school mathematics classrooms for students with learning disabilities. The purpose of this study was to examine the effects of Multimedia Open Resources for Education (MORE) on the mathematics performance and motivation of high school students diagnosed with learning disabilities. The independent variable was the use of three MORE to supplement mathematics instruction. The outcome measures included students' achievement and motivation. At the end of the four-week study, a posttest was conducted, followed by the Course Interest Survey (CIS) based on Keller's ARCS motivational theory. The results showed that the achievement test scores between the experimental group and the control group were not significantly different. However, the results of the CIS showed a statistically significant difference in motivation between the two groups (p < 0.05) in all of the four motivational components - attention, relevance, confidence, and satisfaction.