Consumption of added sugar is a cause of concern due to links with non-communicable diseases. Non-nutritive sweeteners (NNSs) are increasingly seen as a viable alternative. Health and safety of NNSs are well studied, but not their environmental impact. In this study the environmental impact of NNSs aspartame and neotame are presented. This is the first such study attempting to quantify environmental impact of neotame. Life cycle data are derived from literature, alongside stoichiometric reaction equations and resulting heat changes. Global warming potential (GWP) of 1 kg aspartame is found to be 29.25 kgCO₂-eq/kg, and 1 kg neotame to be 43.42 kgCO₂-eq/kg. It is found that both NNSs have great potential to replace the sweetness of added sugar with reduced environmental impact, e.g., GWP of neotame is found to be 0.4–0.7%, and aspartame 10.5–18.4%, of an equivalent sweetness for sucrose. This study demonstrates that environmental impact of the additional resources required to make neotame from aspartame are more than offset by the increase in perceived sweetness, from 200 to 8000-times. It is shown that there are significant uncertainties related to life cycle inventory data and data derivation method. Therefore, this work further highlights the difficulties of conducting a life cycle assessment of highly refined industrial food additives and the need for good industrial collaboration in obtaining data.