This paper examined the effects of online English-medium instruction (EMI) on high school students' performing English face threatening speech acts, by assessing indirect expressions and token agreement (agreement plus but). Participants completed an English placement test and English pretest and posttest through a Google survey. English proficiency, required for study participation was measured using the English placement test. An English pretest and posttest measured English pragmatic performance. The students were given approximately four weeks to complete eight online lectures. The experimental group completed eight online lectures which taught five face threatening speech acts, based on formal situations in the United States. The control group completed eight online lectures about worldwide cultures. The experimental group showed a significant improvement in the English posttest compared with the control group, based on improvements observed in the use of indirect expressions and token agreement. A difference between groups using indirect expressions was observed in an unfamiliar person scenario but not in a familiar person scenario.