Scientific evidence shows that dairy cows fed rations supplemented with 3-Nitrooxypropanol (3-NOP), a potent methane inhibitor, can reduce feed intake. Although the mechanisms underlying this behavioural change are still unknown, reduced feed intake is a typical sign of discomfort. However, the potential welfare effects of this feed additive have not been studied. This study, which built on a larger project examining the effects of 3-NOP on performance and emissions, is the first to examine short-term behavioural responses to 3-NOP and the presence or absence of behavioural signs of discomfort, and contribute to forming the basis for commercially applicable recommendations regarding the use of this additive with higher focus on dairy cow welfare. Evidence on behavioural responses to 3-NOP and investigations of the potential presence of discomfort will provide the scientific basis to guide future research, allowing balanced decision making to be carried out that considers both climate action and animal welfare.