This quasi-experimental study was designed to investigate the initial efficacy of a fraction-vocabulary intervention for Grade 4 students with mathematics difficulty (MD) and to explore its impact on relevant fraction competencies. Thirty-three students were assigned to either the intervention condition (n = 16) or a business-as-usual comparison condition (n = 17). The intervention occurred 3 sessions per week for 4 weeks, for a total of 11 sessions. Results indicated the main effect of the fraction-vocabulary intervention was significant for fraction-vocabulary posttest and one fraction competency—fraction arithmetic. That is, students with MD can successfully learn fraction vocabulary via a brief intervention, and improved fraction-vocabulary knowledge may positively affect their fraction competencies.