Final results showed that voters overwhelmingly supported reforming Swiss gun laws, with 63.7 percent casting their ballot in favour.
A majority of voters in all but one of Switzerland's 26 cantons backed the reform, with the Italian-speaking canton of Ticino in southern Switzerland the only outlier.
A demand from the neighbouring European Union that the Swiss toughen their gun laws prompted a rare national debate over firearm ownership in the country, which has a deeply-rooted gun culture.
While the government cautioned that the new legislation was crucial to the non-EU country maintaining its treaties with the bloc, the proposal sparked a fierce pushback from the gun lobby and shooting enthusiasts, who gathered enough signatures to trigger a vote under Switzerland's famous direct democratic system.
While not an EU member, Switzerland is bound to the bloc through an array of intricately connected bilateral agreements.
Bern had cautioned that a "No" vote would lead to Switzerland's exclusion from the visa-free Schengen travel region and also the Dublin accords regulating Europe's asylum-seeking process.
The shooting enthusiasts behind Sunday's referendum had insisted the government warnings were "exaggerated".
The campaign charged that law change amounts to an "EU dictate" that reins in Swiss sovereignty and would "erase the right to own weapons" in Switzerland.
The ProTell gun lobby voiced concern at the consequences of Sunday's referendum, in which some 43 percent of eligible voters participated.
"Today, our liberties have been eroded," ProTell President Jean-Luc Addor told RTS, also insisting that the reform would "obviously not avoid a single terrorist attack".
The populist, right-wing Swiss People's Party (SVP) – the only party to oppose the reform -- meanwhile cautioned that bowing to an "EU dictate" would have consequences.