In the study, the effect of hierarchical vocabulary activities prepared in accordance with Gass's Second Language Acquisition Model developed by Ates (2016) on students' written expression skills and writing anxiety was investigated. While the determined target words were taught to the experimental group with hierarchical vocabulary activities, the supervised group was kept in a regular diary. The method of the study consists of an experimental design with pre-test-post-test-measurement and supervised group. Experimental and supervised groups consisted of foreign students studying at Inonu-TÖMER in the 2017-2018 academic year. An essay was written to the students as a pre-test and a post-test, and the Writing Anxiety Scale was applied. No significant difference was found between the experimental and supervised groups of the Written Expression Rubric, which is used to score the compositions, in the pre-test and post-tests. It was concluded that the privatized instruction applied to both groups was beneficial for students' written expressions. There was a significant difference between the experimental and supervised groups in terms of Writing Anxiety Scale pre-test scores. It was determined that the writing anxiety of the experimental group was higher in the pre-test.