Despite broad support for policies requiring that prospective firearm owners receive training before acquiring a firearm, little is known about the scope and content of firearm training in the USA. Nationally representative surveys conducted in 1994 estimated that 56%-58% of the US firearm owners had received formal firearm training. We conducted a nationally representative survey in 2015 (n=3932; completion proportion=55%) to update those estimates and characterise training contents. 61% of firearm owners and 14% of non-owners living with a firearm owner reported having received formal firearm training. The most commonly reported combination of training topics was safe handling, safe storage and preventing accidents. 15% of firearm owners reported that their training included information about suicide prevention. The proportion of the US firearm owners with formal firearm training has not meaningfully changed since two decades ago. Training programme contents vary widely. Efforts to standardise and evaluate the effectiveness of firearm training are warranted.