Dozens of towns and cities across Poland are sought to prevent evacuation protests.
Most demonstrations attracted fewer than hundreds on Saturday, but police estimated that around 3,000 people attended the largest rally in the southern city of Katowice.
The protest was organized by far-right political group Konfederacja and another nationalist organisation.
Konfederacja politicians and the opposition law and the judicial party have warned about the flood of illegal migration in Poland, but official figures do not support their claims.
“Without closing Poland to illegal immigrants, without launching a deportation campaign, without abandoning political correctness… security will gradually deteriorate,” Konfederacja co-chair Krzysztof Bosak told crowds in eastern Bialystok.
A one-minute silence was held at several gatherings to commemorate the 24-year-old Polish woman who was murdered in the central city of Torun.
In Warsaw, rival gatherings took place exactly one metre away. There were no reports of violence.
Police later arrested a Venezuelan man in the incident.
Right-wing politicians argue that Poland is at risk of flooding with illegal immigrants.
While immigration has increased over the past decade, official figures show that immigration this year is lower than in the past few years.
Earlier this month, Poland introduced checks on the border between Germany and Lithuania after Berlin stolen asylum seekers. Germany introduced its own control over the Polish-Czech border in 2023.
In March, Poland temporarily suspended the right of immigrants to arrive in the country across the border with Belarus to apply for asylum.
