Opposition demonstrators carried national flags and banners with slogans like "Maduro out" and "Follow Bolivia's example" -- a reference to the resignation of that country's leader Evo Morales in the face of accusations of election fraud.
Guaido, who is recognized as Venezuela's acting president by about fifty countries, was to speak to his backers at Jose Marti square.
"Today is a great victory for Venezuela," Guaido tweeted along with pictures of protesters in other Venezuelan states including Merida, Zulia and Falcon.
"We have come today with very high expectations, we don't want this to be just another march," said Omar Kienzler, a 19-year-old law student.
Guaido, the head of the opposition-dominated National Assembly, has thus far failed to capitalize on early momentum built after he declared himself the crisis-wracked country's acting president in January.
His camp believes that the 2018 elections which returned Maduro to office was undermined by fraud. The opposition leader has urged the leftist leader, the political heir of late president Hugo Chavez, to call new elections.
The numbers of protesters on Saturday seemed a far cry from the tens of thousands he once rallied, but some 5,000 people marched in Caracas, making it the biggest rally since May, after a failed uprising led by Guaido.
"Evo is gone, Maduro is going -- Venezuela shouts, we want freedom!" chanted 65-year-old Rafael Castillo. Protests in Caracas and elsewhere unfolded without incident.
The Venezuelan economy has halved since 2013, as inflation soars and the oil-rich country is subject to crippling US sanctions including an embargo on crude.
"If nothing major happens, Guaido's leadership will end up on ice," political analyst Jesus Castillo-Molleda told AFP.
A recent poll by the Delphos firm showed that 38 percent of opponents to Maduro want a new leader to emerge.
In downtown Caracas, hundreds of Chavistas dressed in red mobilized in support of Maduro and Morales.
Maduro has warned that he will not tolerate any effort to replicate what he calls the "coup d'etat" that ended with Morales' departure into exile in Mexico.
On Friday, armed men stormed Guaido's party headquarters in the eastern part of Caracas, taking security cameras and computers, money and ID documents.
In La Paz on Saturday, interim Bolivian leader Jeanine Anez called on Guaido to "liberate" Venezuela.
"It's unfair that you have suffered through so much violence and repression," she said in a video message broadcast live on national television.