The aims of this study were (1) to explain the effectiveness of learning to write invitation letters using a project based learning model for fifth grade elementary school students, (2) to explain the effectiveness of learning to write invitation letters using an expository model for fifth grade elementary school students, (3) to find out differences in the level of the effectiveness of learning to write invitation letters with project based learning models and expository models for fifth grade elementary school students. The research designs used in this study were quasi-experiment designs. The results of this study 1) Learning to write invitation letters with a project based learning model had an effect on increasing learning outcomes in writing invitation letters for fifth grade elementary school students, 2) Learning to write invitation letters with an expository model had an effect on increasing learning outcomes in writing invitation letters at fifth grade elementary school students, 3) learning to write invitation letters with an expository model was better than project based learning model learning in improving learning outcomes to write invitation letters for fifth grade elementary school students. Keywords: Learning to write invitation letters, project-based learning models, expository models.