Several speakers led by the head of a support group for the unemployed spoke at Hong Lim Park on Thursday, lashing out at what they described as pro-foreigner policies and the high influx of foreign workers.
The Labour Day protest organised by Mr Gilbert Goh lasted three hours, with many speakers stressing they were not being xenophobic, and that their main interest lay in protecting Singaporean workers.
"We want to give workers a chance to voice out their grievances, I think there are many", said Mr Goh, 53, the founder and president of Transitioning.org.
"When you speak out for your country, if you're branded a xenophobe, I don't know what to say. I'm doing this all for my country."
In the lead-up to the event, Mr Goh, claiming that Prime Minister Lee Hsien Loong sided with foreigners, said on Facebook that he would put up a picture of the Prime Minister at the protest and invite protestors to kick at and deface it, among other things.
But this did not materialise, after Mr Goh received a police warning on Wednesday that these acts may constitute offences under the Penal Code and the Miscellaneous Offences (Public Order and Nuisance) Act.