India's biofuel programme relies on ethanol production from sugarcane molasses. However, there is limited insight on environmental impacts across the Indian ethanol production chain. This study closes this gap by assessing the environmental impacts of ethanol production from sugarcane molasses in Uttar Pradesh, India. A comparative analysis with south-central Brazilian sugarcane ethanol is also presented to compare the performance of sugarcane molasses-based ethanol with sugarcane juice-based ethanol. Methods The production process is assessed by a cradle-togate life cycle assessment. The multifunctionality problem is solved by applying two variants of system expansion and economic allocation. Environmental impacts are assessed with Impact 2002+ and results are presented at the midpoint level for greenhouse gas emissions, non-renewable energy use, freshwater eutrophication and water use. Furthermore, results include impacts on human health and ecosystem quality at the damage level. Sensitivity analysis is also performed on key contributing parameters such as pesticides, stillage treatment and irrigation water use. Results and discussion It is found that, compared to Brazilian ethanol, Indian ethanol causes lower or comparable greenhouse gas emissions (0.09–0.64 kgCO2eq/kgethanolIN, 0.46–0.63 kgCO2eq/kgethanolBR), non-renewable energy use (−0.3–6.3 MJ/kgethanolIN, 1–4MJ/kgethanolBR), human health impacts (3.6·10−6 DALY/kgethanolIN, 4·10−6 DALY/kgethanolBR) and ecosystem impairment (2.5 PDF·m2·year/kgethanolIN, 3.3 PDF·m2·year/kgethanolBR). One reason is that Indian ethanol is exclusively produced from molasses, a co-product of sugar production, resulting in allocation of the environmental burden. Additionally, Indian sugar mills and distilleries produce surplus electricity for which they receive credits for displacing grid electricity of relatively high CO2 emission intensity. When economic allocation is applied, the greenhouse gas emissions for Indian and Brazilian ethanol are comparable. Non-renewable energy use is higher for Indian ethanol, primarily due to energy requirements for irrigation. For water use and related impacts, Indian ethanol scores worse due groundwater irrigation, despite the dampening effect of allocation. The variation on greenhouse gas emissions and non-renewable energy use of Indian ills is much larger for high and low performance than the respective systems in Brazil. Conclusions Important measures can be taken across the production chain to improve the environmental performance of Indian ethanol production (e.g. avoiding the use of specific pesticides, avoiding the disposal of untreated stillage, transition to water efficient crops). However, to meet the targets of the Indian ethanol blending programme, displacement effects are likely to occur in countries which export ethanol. To assess such effects, a consequential study needs to be prepared.