This study examined how smart device applications affected elementary school students who have learning difficulties in English. Five 6th grade students who needed remedial instruction were selected and given 50 hours of instruction using English vocabulary flash cards in a smartphone application. one hundred vocabulary words were chosen and developed for flash cards for the students to examine their intellectual and emotional changes in English learning. The research results showed that the students' vocabulary improved in listening, reading and speaking. It also revealed that the students gained confidence and interest in English learning, and their anxiety decreased. In addition, the application was easy and convenient for the students to use, especially in recognizing the pronunciation and the meaning of the vocabulary words. This study recommends further development and use of smart device applications for elementary school English instruction.