Writing is a crucial skill for students to support their academic lives as it pertains to many course materials taught in the class. However, many studies found that students still face difficulties in writing, one of which is related to vocabulary knowledge. This quantitative research examined whether there is a significant correlation between students’ vocabulary knowledge and their writing skills. A test consisting of multiple-choice and essay questions was administered to 60 11th grade students. The Pearson Product Moment Test yielded a ρ-value of .0004, indicating a correlation between vocabulary knowledge and writing skills as measured by scores (ρ ≤ .05). The positive correlation coefficient of r count (r = .436) was found to be greater than the r table of .254 (Df 58 at .05 2-tailed level). Based on this r count, the significance level is considered moderate (See Table 1 in Chapter III). Thus, it can be concluded that an understanding of vocabulary is just one of many aspects that can influence students’ writing skills. Therefore, teachers are expected to be one of the bridges that can facilitate students in learning vocabulary.