Brazil is the largest world producer and consumer of coconut water with approximately two billion fruits, where 70% is for water production. Therefore, a large amount of waste is generated: the coir husk, which represents approximately 1.75 kg per fruit unit. This biomass presents 35% cellulose in its composition, which makes the coir husk a good option for the raw material for second-generation (2 G) ethanol production. In this study, the coir husk was chemically pretreated using four different treatments. The 2 G ethanol production was studied considering two different processes, using separated hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The pretreatment used a solution containing sodium chlorite at 10% of the acetic acid and the SSF process was the better method for 2 G ethanol production from coir husk, yielding 52.7 L ethanol/ton of biomass. Thus, the coir husk can be considered an alternative for the production of 2 G ethanol, with all the environmental and social advantages of such an approach, such as occupying precious space in the landfills and taking 12 years to decompose.