President Oscar Berger said he hoped the move would cut the number of shootings in the country.
It would not produce major results in the short term, he said, "but together we will resolve, little by little, the problems of violence in Guatemala".
At least 1,600 people have been shot dead in the central American country since the start of the year.
Guatemalans are permitted by their constitution to carry arms, but it is thought there may be 10 times as many weapons in the country as the 200,000 officially registered.
Mr Berger smashed a rifle with a hammer during the ceremony to launch the campaign.
Schoolchildren sang songs and wore T-shirts saying "Live peace, live without arms".
To back up the amnesty offer, the government has promised a crackdown on the manufacture and smuggling of weapons, and has launched a public awareness campaign.
The president said people could hand in their arms at regional centres, and would receive goods like bicycles, sewing machines and roofing materials in return.
The government is set to invest 1m quetzals (£67,000) in the first stage of the programme, to buy the household appliances to swap for guns.
Guatemala, a country of 12 million people, signed peace accords in 1996 after three decades of civil war.