Certified Reference Materials (CRMs) are a widely recognized tool for the comparability of measurements taken in different times and spaces through their “traceability chain”. However, aqueous CRMs used as calibrants which allow tracing to the SI units are urgently needed especially for the speciation analysis CRMs due to the difficulty of development and certification for them. Herein, we presented two new aqueous trimethyllead reference materials. In the certification campaign, two important steps were included: 1) a traceability chain to the standard reference material GBW08619 which is a primary Pb(II) calibrant solution was set up; 2) isotopic variations of lead in trimethyllead (TML) and GBW08619, were introduced to the certified values and combined uncertainties. This paper describes in detail the homogeneity and stability studies, impurity assessment with nuclear magnetic resonance spectroscopy (NMR) and high-performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICP-MS), traceability assurance protocol and the inter-laboratory co-certification campaign for the certification of their TML contents. Consequently, two CRMs (GBW(E)080971: (92.73±3.15) μg g-1 as Pb, k=2 and GBW(E)080972: (0.740±0.030) μg g-1 as Pb, k=2) are now available.