The short story The Last Leaf is an old short story written by O. Henry, one of the greatest short stories author in America. This short story also has been adapted in the big screen so it is a proof that this story is inspiring and has a good moral value. In this study, the researcher conducted a research on the short story The Last Leaf by O. Henry by using transitivity analysis. There are three objectives of this research: to identify the ideational meanings realized in the short story The Last Leaf, to describe the messages represented through the ideational meanings in the short story The Last Leaf , and to explain the contribution of the analysis of this short story to the teaching and learning process of the discourse analysis subject. This study used a qualitative research design which uses the documentation to collect the data. Regarding the result of data analysis, there are six processes found in the short story The Last Leaf by O. Henry. They are material (40.29%), relational (19.71%), verbal (15.14%), mental (12.57%), behavioral (9.43%), and existential (2.86%). The dominant process of this short story is the material process. The material processes occur 141 times (40.29%), which means the author used the material processes most frequently to tell what happened to the characters or what the characters do in developing this short story. Although the author used the material process dominantly, the author still needs the other process types to develop this short story. The result of this study contributes as the teaching media for teaching learning process in the discourse analysis subject.