Neuromelanin (NM) MRI has received increasing interest in applications to diagnosis of Parkinson’s disease. A reduction of T1 associated with paramagnetic melanin-iron complexes is assumed to be the primary contrast mechanism. NM is able to chelate large quantities of iron but also, to a lesser extent, other transition metals, in particular copper. Here, we investigated the effect of different copper/iron concentrations bound to NM on water T1 and T2. Our results corroborate previous studies suggesting a concentration-dependent decrease of T1 for iron-loaded melanin. Additionally, we found a synergetic effect if both metals are simultaneously present leading to a pronounced T1-shortening.