Research has shown that natural gas (NG) has a significant negative impact on the climate. The role of NG in future global energy systems is highly controversial. Due to the greenhouse gas emissions associated with NG and the potential delay of low-carbon technologies, this energy source could represent a barrier rather than a solution to successful sustainability transitions. However, it appears that very little existing research covers NG-related risks for energy transitions. This paper covers a systematic mapping of the academic sustainability transitions literature, compiling existing evidence on the potential risks and adverse effects of using NG. Methane emissions in particular pose large climate risks, while the main barriers to sustainability transitions caused by NG include a crowding-out effect of low-carbon technologies, stranded assets, infrastructure lock-in, and behavioural lock-ins. The resulting political challenges include achieving climate mitigation targets, dealing with opposition to NG reduction, and addressing discursive lock-ins. The studies cited here highlight the fact that the potential of NG to reduce greenhouse gases is small, and that climate targets cannot be achieved via NG use in the long term.