There are several factors affecting students’ test performance in English as a foreign language (EFL) writing. This paper focuses on “motivation” as one of these factors and investigates why and how it influences student performance in writing by reviewing the literature. In recent years, a number of studies have been conducted to examine writing motivation and some variables that increase motivation hence students’ writing performance. Thus, it can be concluded that there is a positive relationship between motivation and writing. Students who have higher intrinsic or extrinsic motivation perform better than those who do not. Creating a learner-centered writing environment and choosing the writing tasks properly affect both motivation and performance. As a result, EFL teachers can try out new methods and materials to teach and test writing in a way that will foster their students’ writing motivation. In this way, they cannot only help the students gain positive attitudes towards writing but also provide curriculum developers and policy makers with feedback in order for them to include motivational aspects in EFL writing courses and tests.