Grit entails working strenuously and staying highly interested even in the face of setbacks in order to reach long-term goals. Grit has been discussed as potential predictor and determinant of academic performance. The present study investigated the relationship between grit, self-regulated learning (SRL), and achievement in the context of writing a larger and complex scientific paper, the “Maturaarbeit”. We surveyed several times 1215 upper secondary school students (grad 11/12; ISCED level 3) during the one-year period of writing the Maturaarbeit. Structural equation modeling revealed perseverance of effort as a consistent predictor for all indicators of SRL including metamotivational knowledge, motivational regulation strategies, and cognitive regulation competencies. Consistency of interest positively correlated with cognitive regulation competencies, however, showed a negative correlation on the self-reported use of motivational regulation strategies. Further, we found significant indirect effects of grit on students` achievement above SRL competencies. However, only perseverance of effort predicted achievement before, and after accounting for SRL. The results of this study indicated that, in addition to cognitive skills and the engagement in learning activities, the ability to use these skills persistently over time is supporting the achievement of challenging goals. Further, the result indicated that perseverance of effort and consistency of interest showed different incremental validity.