Five referendums were held in Switzerland during 1920. The first three were held on 21 March on a federal law on regulating employment contracts, a ban on creating gambling establishments and a counterproposal to the ban. The fourth was held on 16 May on membership the League of Nations (which Switzerland had become a founding member of the previous year), whilst the fifth was held on 31 October on a federal law on working times on railways and other transport services. Of the five, only the ban on gambling establishments, League of Nations membership and the law on working times were passed.
The referendum on joining the League of Nations was a mandatory referendum, whilst the ban on gambling establishments was a popular initiative. Together with the counter-proposal, all three required a double majority; a majority of the popular vote and majority of the cantons. The decision of each canton was based on the vote in that canton. Full cantons counted as one vote, whilst half cantons counted as half. The referendums on employment contracts and working times were optional referendums, which required only a majority of the public vote.