NMR spectroscopy of paramagnetic metalloproteins has been historically disfavored based on the fast nuclear relaxation rates induced by unpaired electrons, which leads to extreme line broadening and impairs magnetization transfer. Recent advances in the application of state-of-the-art pulse sequences are described herein, with particular emphasis on copper proteins, which present unfavorable electron relaxation times. In the case of binuclear copper centers, NMR is particularly useful for obtaining information on the electronic structure of partially populated (invisible) excited states which determine their reactivity.