This study examines a linkage between the international mathematics scale of the Programme for International Student Assessment (PISA 2012) and the mathematics assessment taken from the German National Educational Panel Study (NEPS). The linking was realized by a separate linking study that uses a single group design. The sample consists of n = 1,270 9th graders from 78 German secondary schools. The equipercentile linking leads to close descriptive scale characteristics (means, standard deviation, and skewness) between the original PISA mathematics scale and the PISA score equivalents. The linking was stable over the four subgroups (gender, migration background, books at home, and school type). Altogether, the results indicate that assigning students to PISA proficiency levels given their NEPS mathematics test score, the PISA score equivalents produce a similar distribution of students reaching the PISA proficiency levels at a group level.