The inhibition efficiency of a scale inhibitor, named diethylene triamine penta (methylene phosphonic acid) (DTPMPA), was evaluated using fast controlled precipitation (FCP) method, electrochemical quartz crystal microbalance (EQCM), quartz crystal microbalance with dissipation (QCM-D) and pre-scaled quartz crystal microbalance (SQCM). The results showed that DTPMPA delayed the CaCO3 precipitation and decreased the precipitation rate of the CaCO3 formation in solution and on a metallic surface, depending on the inhibitor concentration. In some cases, it could completely inhibit CaCO3 formation. CaCO3 precipitation was completely inhibited in solution and on a metallic surface in the presence of 0.5 mgL–1 and 4 mgL–1 DTPMPA, according to FCP and EQCM results, respectively. The morphology and composition of CaCO3 crystals formed were studied using SEM and XRD showing that the presence of the inhibitor promoted the formation of calcite. This is the first time that the influence of an organic inhibitor was studied using the combination of QCM methods, where the results revealed a reduction of the surface coverage by a CaCO3 layer as the inhibitor concentration increased. The activation energies were calculated in the presence of DTPMPA and indicated that the inhibitor retarded the scaling process.