The opposition march had to be re-routed
Massive security was in place to prevent clashes between the rival demonstrations, which marked the anniversary of the country's transition to democracy in 1958.
The marches on Wednesday passed off peacefully on the rain-soaked streets.
A 36-hour ban on carrying guns was announced ahead of the demonstrations.
Opponents of the leftist president and his "peaceful revolution" banged pots and pans and waved Venezuelan flags and placards reading: "Chavez resign".
The president's supporters held a counter-march four blocks away and the two groups were separated by about 3,000 police and National Guard officers.
Opposition unites
Mr Chavez joined the march, wearing his trademark red beret, and was mobbed by supporters.
In a fierce speech that, by law, had to be broadcast by all Venezuelan radio and television stations, Mr Chavez accused the independent news media of inflating the size and importance of the opposition march and of "sowing hate" among Venezuelans.
He said his "march of the patriots" had defeated "the march of the filthy ones" led by an opposition "mafia".
Anti-Chavez organisers were hoping to draw together trade unionists, business leaders, conservative political parties and civil rights groups in protest at the president's sweeping reform programme.
They had to re-route their march after the president announced a counter-demonstration and the two looked set to meet outside Congress.
"We want Chavez out of office. We don't need him, he is crazy," growled one marcher.
Opposition groups attack the populist former army officer's attempts to tackle corruption and redistribute wealth as authoritarian, saying he is eroding the civil rights gained when General Marcos Perez Jimenez was ousted in an uprising 44 years ago.
They also say his strong criticism of the press has led to attacks on journalists.
Reforms feared
"I voted for Chavez but I feel betrayed," said Arquimedes Gonzalez, a shopkeeper from the northern state of Sucre.
"We have to defend the democracy that we built after we ousted Perez Jimenez."
But government supporters say opposition protests are the country's elite digging in their heels against reforms which will hit their pockets.
"We came in solidarity with the president's call," said one marcher, also wearing a red beret.
"We share the ideals of a sovereign country, free and independent and living in equality."
Defence Minister Jose Vicente Rangel, also in the government march, said: "This is the best proof that we are living in a real democracy where people can demonstrate."
Mr Chavez was elected president of Venezuela, the world's fourth largest oil exporter, in 1998, six years after he led a failed coup attempt.
His action-man image and revolutionary rhetoric were initially well received among the 24 million Venezuelans living in poverty.
General strike
But he split the country along class lines and his approval rating dropped from 60% in January last year to 35% in December.
Last month, millions of Venezuelans staged a general strike in protest against 49 laws imposed under special decree, including an unpopular land law allowing the government to seize and redistribute land deemed unproductive.
Mr Chavez has also recently introduced laws giving the state a stake in all new oil ventures and almost doubling the royalties oil companies must pay.