Prior research has consistently shown that motivation is a catalyst for students' writing performance, with important implications for writing instruction. However, this body of research has mainly relied on a variable-centered approach that does not acknowledge the similarities and differences between and within groups of students. In the current study, we sought to address this research gap by examining the association between different motivational profiles and writing performance using a person-centered approach. Accordingly, we aimed to: (1) identify different motivational profiles in writing, based on students' implicit theories and achievement goals; and (2) examine whether students in different profiles varied in writing performance. To this end, we sampled 212 Portuguese sixth-grade students (M = 11.11 years, SD = 0.56) and collected motivational and writing performance measures at a single time point. Cluster analyses revealed two distinct writing motivation profiles: one profile reflected students with a growth mindset who were less oriented toward performance-approach and performance-avoidance goals, and another profile represented students with a fixed mindset who were more oriented toward performance-approach and performance-avoidance goals. Subsequent analyses indicated that one profile could be considered as more adaptive than the other. Specifically, students in the growth mindset and less performance-oriented profile wrote opinion texts with better quality and earned higher writing grades than students in the fixed mindset and more performance-oriented profile. Overall, these findings suggest that teachers should add motivation-enhancing practices to writing instruction and tailor their teaching practices according to students' unique motivational profiles.