The room temperature growth kinetics of the commonly studied metal-organic framework CuBTC (HKUST-1) is investigated with UV/vis absorption spectroscopy. Contrary to chemical intuition, increased concentrations of the BTC ligand slows down the formation of CuBTC. Based on the time-resolved experimental data, a kinetic model is proposed for CuBTC growth. This model is based on a chemical reaction equation sequence for the production of CuBTC including an overcoordinated, slowly reacting Cu-BTCx species. This growth model excellently captures the temporal CuBTC development over the entire range of concentration conditions.