This research is motivated by the constraints of students in writing biographical texts using appropriate, complete, correct linguistic structures and elements, and low interest in writing, because so far no studies have been carried out to find suitable learning models. Therefore, it is necessary to analyze the effect of the application of the Numbered Head Together (NHT) cooperative learning model on the writing skills of biographical texts, as a solution to improve students' writing skills. This type of research is quantitative using experimental methods. The design is one group pre-test and post-test design. The population is class X students of SMA N 1 West Sumatra Padangpanjang who are registered for the academic year of 2020/2021. Sampling was done by using the purposive sampling technique. Research data, namely the performance test scores for writing biographical texts before and after applying the NHT cooperative model. Based on the results of the t-test, the application of the NHT type cooperative model affects the students' biographical text writing skills at a significance level of 95% with dk = n − 1, t table < t count (13.83 < 8.96). Thus, the skill of writing a biographical text after applying the NHT type cooperative model is better than before. It means that the cooperative learning model of the NHT type can improve the process and learning outcomes of students' biographical text writing skills.