This research was carried out in order to prove whether the use of transcription technique was effective in improving the ability in pronouncing English vowel sounds of the eleventh grade students at SMA Negeri 5 Palu. This research applied intact research design thatused two classes. They were experimental group and control group. The research population was the eleventh grade students at SMA Negeri 5 Palu. The sample of this research was taken by using opportunity sampling. The number of students of this research was 62 students. The data of the research were collected by giving post-test to both experimental and control groups. The data were analyzed by using statistical analysis in order to know the significant difference achievement of the students in post-test. The result of data analysis showed that there was a significant difference between post-test result in both experimental and control groups. By applying two-tailed test at 0.05 level of significance with60 degree of freedom (df) or 62-2= 60, the researcher found that t-counted (10.13) was greater than t-table (2.000). It could be concluded that the research hypothesis was accepted. In other words, the use of transcription can improve pronunciation of the eleventh grade students at SMA Negeri 5 Palu.