Switzerland as a whole has no minimum wage, and voters in 2014 turned down a chance to adopt one at a national level.
Geneva voters themselves have twice previously rejected calls to introduce a minimum wage in the city.
But on Sunday the winds appeared to have changed as the coronavirus pandemic has deepened the wealth gap, with 58 percent of voters in the canton coming out in favour of the unions-backed initiative.
The result made Geneva the third of Switzerland's 26 cantons to set a minimum hourly earnings rate after Jura and Neuchatel.
The initiative, which had the support of all the left-leaning parties, had been presented as a remedy to poverty and precariousness, which have become increasingly visible in wealthy Geneva since the coronavirus crisis began.
Long lines of people waiting for handouts of food and other necessities have become a common sight in the city.
The unions behind the initiative argued that it was impossible in Geneva to live in dignity making less than 23 Swiss francs ($25, 21 euros) an hour, or 4,086 francs a month for a full-time 41-hour work week.
Rent for a typical two-bedroom apartment is at least 3,000 francs, and a coffee costs four or five francs. Geneva's minimum wage vote was just one of many national, regional and local issues on the ballot Sunday as part of Switzerland's famous direct democratic system.
At a national level, voters appeared poised to make history on another social issue by approving paternity leave for the first time in the country long renowned for its traditional approach to family models and gender roles.
That referendum to grant new fathers two weeks paid leave looked set to pass with nearly 57 percent of the vote at the national level, according to partial results, while full results in Geneva showed the canton backing the measure by over 79 percent.
Highest in the world
This is well above the current highest minimum wage in the world, which is Australia’s $19.84 per hour (CHF13.15).
Over a 40-hour work week, this adds up to 4,100 francs per month. The average wage in Switzerland is currently CHF6,500.
A cantonal vote on implementing a minimum wage was knocked back by 54 percent of the electorate in 2011, while a similar vote at the federal level was rejected by 66 percent of the electorate in 2014.
According to Swiss news outlet Le Temps, the coronavirus pandemic may play a key role in changing the outcome of the vote.
Two Swiss cantons – Neuchâtel and Jura – have put in place minimums, while Ticino has recently approved a minimum via a referendum, but hasn't yet put it into law.
Basel will also go to the polls on a minimum wage of 23 francs, however a date for the vote has not been set.