A monthly guaranteed salary of 2,500 francs would fight poverty and provide "a dignified" existence for all, according to campaigners.
The Swiss government and nearly all the country's political parties have urged voters to reject the controversial initiative, advice 72 percent are inclined to follow, according to the latest poll.
Critics have slammed the initiative as "a Marxist dream", warning of sky-high costs and people quitting their jobs in droves.
"If you pay people to do nothing, they will do nothing," Charles Wyplosz, economics professor at the Geneva Graduate Institute, told AFP.
Proponents reject that, arguing people naturally want to be productive, and a basic income would simply provide them with more flexibility to choose the activities they find most valuable.
"For centuries this has been considered a utopia, but today it has not only become possible, but indispensible," Ralph Kundig, one of the lead campaigners, told AFP.
Sunday's vote is on the principle only, and doesn't fix the amount, the financing, or the conditions.
However UBI supporters would like all Swiss citizens to get the monthly payment, as well as foreigners who have been legal residents for at least five years.
So we want to know what you think. How would you vote, if you could?
Make your choice with our interactive poll and let us know your thoughts in the comments section below.