|Plazo de Mayo, Buenos Aires where the presidential palace is located|
The protest was called by federal prosecutors and attended by Mr Nisman's family and opposition politicians.
They defied torrential rain to demand justice for Mr Nisman, who had been investigating the government.
The prosecutor was found dead in his apartment on 18 January.
It is still not clear whether he killed himself or was murdered.
Mr Nisman was investigating Argentina's deadliest terrorist attack, the 1994 bombing of the Amia Jewish centre.
The silent march was called by prosecutors demanding a full investigation.
Mr Nisman's ex-wife, federal judge Sandra Arroyo Salgado, and their two daughters joined the demonstration, which lasted nearly two hours.
Similar protests took place across the country.
|Murdered prosecutor Alberto Nisman|
Officials have denounced the march as a political move to weaken the government.
Mr Nisman was found with a bullet wound to the head and a gun was lying next to him.
Days earlier, he had published a 300-page report in which he accused President Cristina Fernandez de Kirchner and Foreign Minister Hector Timerman of covering up Iran's alleged role in the bombing.
|President Cristina Fernandez de Kirchner|
News of his death and its timing led to speculation among some Argentines that the government may have played a role in it.
The government has strongly denied both allegations.
In an open letter published on her website, President Fernandez suggested rogue intelligence agents had fed Mr Nisman false information in order to destabilise her government.
She also said she was convinced Mr Nisman's death was not suicide.
Days later, she announced she planned to dissolve Argentina's intelligence service, SI.
Critics said the move was aimed at diverting attention away from Mr Nisman's death.
In fact, it was a good move by the much beleaguered, but always elegant President. If rogue elements had been involved in planting false information, or even in the death of Mr Nisman, then they had to be cut down.
On the other hand, if they had been acting on behalf of the President (whether she knew it or not), and murdered Nisman, they did such an amateur job of it, they deserved to be fired. I would think a country the size of Argentina would have a secret service capable of doing a better job of murdering someone.
Earlier, President Fernandez and her cabinet attended an unrelated event at the Atucha power plant, in the city of Zarate, 90km (55 miles) north of the capital.
Ms Fernandez said she would not bow to internal or external pressure and would remain in office until December, when her term ends.
"This government will not allow anyone else to impose their rules on us," she said in a speech that was broadcast on national television.