The complexes formed between Pb 2+ and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) were reinvestigated in aqueous solutions using a combination of pH potentiometry, UV–vis spectroscopy, and NMR spectroscopy. The thermodynamic data were supported by kinetics assays. Differently protonated complexes, i.e ., [PbH 3 L] + , [PbH 2 L], [PbHL] − , and [PbL] 2– , were detected, and the corresponding stability constants (log β ) at T = 298 K and I = 0.1 M NaCl were 33.1 ± 0.2, 32.00 ± 0.06, 29.28 ± 0.06, and 25.3 ± 0.1, respectively. Results differed significantly from those previously reported by Chaves et al. ( 18965370 Talanta 1992 39 249 ) and Pippin et al. ( Inorg. Chim. Acta 1995 239 43 ) in both the speciation and the overall complex stability; the latter in particular was found to be remarkably higher. The work disclosed herein provides revised data on the Pb 2+ -DOTA complexes, which should be used as a new stability benchmark during the development of lead chelators.