Supporters had said introducing a monthly income of 2,500 Swiss francs ($2,563) per adult and 625 francs per child under 18 no matter how much they work would promote human dignity and public service.
Opponents, including the government, said it would cost too much and weaken the economy.
Provisional final results showed 76.9 percent of voters opposed the bold social experiment launched by Basel cafe owner Daniel Haeni and allies in a vote under the Swiss system of direct democracy.
Haeni acknowledged defeat but claimed a moral victory.
"As a businessman I am a realist and had reckoned with 15 percent support, now it looks like more than 20 percent or maybe even 25 percent. I find that fabulous and sensational," he told SRF.
"When I see the media interest, from abroad as well, then I say we are setting a trend."
Conservative Switzerland is the first country to hold a national referendum on an unconditional basic income, but others including Finland are examining similar plans as societies ponder a world where robots replace humans in the workforce.
Olivier, a 26-year-old carpenter who works on construction sites and runs a small business designing and building furniture, said he voted "yes".
"For me it would be a great opportunity to put my focus on my passion and not go to work just for a living," he said.
Champions of the plan portrayed a more automated future in a poster bigger than a soccer field asking "What would you do if your income was secure?" They had also marched as robots down Zurich's high street and handed out free 10-franc notes.
"I voted 'yes' because money does not really have its place in this world, it is so arbitrary and linked to power games," said Ronnie Lehmann, 37, who makes less than 4,000 francs a month as a bicycle mechanic. "But I'm not surprised the proposal got rejected, the world is not ready for it yet."
A woman named Meleanie said she reluctantly voted "no".
"I find that it is a real danger that once people just get their basic needs covered society doesn't feel responsible any more to look after the ones who can't really handle the situation on their own", she said.
In a separate vote on Sunday, Swiss voters clearly rejected a proposal to require state-controlled companies, such as Swisscom, not to seek to make a profit.
The government had warned that accepting the initiative would hurt the companies' competitiveness and could lead to higher taxes.
Employers heaved a sigh of relief that Switzerland, where unemployment is only around 3.5 percent, had not become the first country to embrace the guaranteed income measure.
The Swiss government had urged voters to reject the campaign, saying the scheme would cost too much and undermine social cohesion.
Interior Minister Alain Berset said the vote showed Swiss voters supported the economic and social system in place "and that this system works well."
The plan included replacing in full or in part what people got from social benefits.
The government estimated the proposal would have cost 208 billion Swiss francs a year, significantly weakened the economy and discouraged people, especially low earners, from working.
Much of the cost could have been covered by existing social security payments, but sharp spending cuts or tax increases would have had to make up a remaining gap of 25 billion.
An advanced social safety net already supports people who cannot pay for their own livelihood. Fewer than seven percent of people lived in poverty in 2014, official data show.
© Thomson Reuters 2016