We report the synthesis of HKUST-1 (Cu3(btc)2; btc=benzene-1,3,5-tricarboxylate) and its growth kinetics by dynamic light scattering completely at room temperature without prior nucleation-induction steps. Upon an increase in concentration of the starting solutions, the generation of a pure phase requires adjustment of the H2O/EtOH ratio. The presence of DMF is important to avoid competitive side phases. Replacement of DMF by a minimal amount of diethylamine resulted in the instantaneous formation of pure HKUST-1 upon mixing at room temperature. Additionally, the synthesis parameters strongly influence the final crystallite size and porous properties.