<p>It is unknown how achievement goals, self-efficacy, and motivation regulation are interrelated and how they together influence L2 writing achievement. The current study adopted a person-based approach and explored the nexus among L2 student writers’ achievement goals, self-efficacy, and motivation regulation and the joint effects on their writing achievements. A total of 416 tertiary students from Southwest China were recruited as voluntary participants. Their achievement goals, writing self-efficacy, and motivation regulation strategies were measured with the Writing Achievement Goals Scale, the Genre-Based L2 Writing Self-Efficacy Scale, and subscales of the Writing Strategies for Self-Regulated Learning Questionnaire, respectively. Their writing achievements was measured with two tasks: argumentative and narrative writing. Latent profile analyses revealed four profiles of achievement goals: “Low All Goals”, “Mastery High”, “Average All Goals”, and “High All Goals”. ANOVA and Welch’s Test results further showed that the participants assigned to these four profiles differed in writing achievement goals, writing self-efficacy, motivation regulation strategies, and writing achievement in the narrative task. Additionally, multiple regression analyses revealed that their profiles varied in the predictive effect of writing self-efficacy and motivation regulation strategies on writing achievements. Methodological and pedagogical implications were also discussed.</p>