This research focused on the ability of writing argumentative text correlate to writing motivation and grammatical competence. This research used survey method through correlational study. It was conducted on the students of grade X in SMA Negeri 3 Serang in academic year 2016/2017 using simple random sampling technique. The data collection in this research were tests to get the data of writing argumentation ability and grammatical competence, while the questionnaire with Likert scale is used to get the data of students' writing motivation. The collected data were analyzed descriptively and inferentially. The data was analyzed using SPSS program version 22.00. Prior to hypothesis testing, several requirements were done: 1) normality test by using Lilliefors technique; 2) linearity test using F test; and 3) correlation test of product moment correlation from Pearson. The results prove: 1) the correlation coefficient (rx1y) shows that the r[subscript count] is higher than the r[subscript table] (0.585> 0.245). Therefore the first hypothesis is accepted; 2) the correlation coefficient (rx2y) shows that the r[subscript count] is higher than the r[subscript table] (0.786> 0.245). This means that the second hypothesis is accepted; and 3) the F[subscript count] coefficient 9,421> F[subscript table] 4.07. Based on the test results, Pvalue 0.000 is lower than 0.05. The conclusion is that the motivation of writing (X[subscript 1]) and grammatical competence (X[subscript 2]) has a positive and significant relationship with the ability to write argumentative text (Y). [This paper was published in: "Advances in Social Science, Education and Humanities Research, Volume 263" (pp. 239-243). Atlantis Press.]