The concept of voice is included in various writing textbooks, learning standards, and assessment rubrics, indicating the importance of this element in writing instruction and assessment at both secondary and postsecondary levels. Researchers in second language (L2) writing, however, often debate the importance of voice in L2 writing. Due to the elusiveness of this concept, much of such debate is still at the theoretical level; few empirical studies exist that provide solid evidence to either support or refute the proposition that voice is an important concept to teach in L2 writing classrooms. To fill this gap, the present study empirically investigated the relationship between voice salience, as captured by an analytic rubric, and official TOEFL iBT argumentative essay scores in 200 timed L2 essays. Results showed that voice was a significant predictor of TOEFL essay scores, explaining about 25% of the score variances. Moreover, while each individual voice dimension was found to be strongly or moderately correlated with essay scores when examined in isolation, only the ideational dimension became a significant predictor of text quality, when the effect of other dimensions was controlled for. Implications of such results for L2 writing instruction are discussed.