In magnetic drug targeting a chemotherapeutic agent is bound to coated magnetic nanoparticles, which are administered to the blood vessel system and subsequently focused by an external applied magnetic field. The optimization of intra-arterial magnetic drug targeting (MDT) requires detailed knowledge about the biodistribution of particles in the artery and the respective surrounding after the application. Here, we demonstrate the potential of magnetorelaxometry for quantifying the distribution of magnetic nanoparticles in the artery. To this end, we present a magnetorelaxometry investigation of a MDT study in an artery model. In particular, the absolute magnetic nanoparticle accumulation along the artery as well as the uptake profile along the region around the MDT-magnet position was quantified.