Prime minister Enrico Letta said the "Safe Seas" mission would start Tuesday south of Sicily.
"The Mediterranean is our sea and we cannot tolerate the deaths that have been taking place in it," he said.
Italian defence minister Mario Mauro said the country intended to triple its presence in the southern Mediterranean.
This had become necessary "in part by the fact that Libya - where many of the people-smuggling boats leave from - is currently a non-state", he told Italian newspaper Avvenire.
"We need strong action to stop these shipwrecks," he added.
Italian media reported that unmanned drone aircraft based in Sicily could also be used to identify boats in trouble.
A European Union summit Oct 24-25 is due to discuss proposals put forward by the executive last week to create a Mediterrean-wide search and rescue mission by the EU borders agency Frontex.
European home affairs commissioner Cecilia Malmstroem announced the plan last week after more than 360 migrants drowned off the Italian island of Lampedusa when their overcrowded boat caught fire and sank Oct 3.
At least 33 people died Oct 11 when their boat capsized between Malta and the Italian island of Lampedusa, prompting Malta's prime minister to claim the Mediterranean was becoming a "cemetery".
Italy has previously called for EU help in dealing with the thousands of desperate migrants who reach its shores by boat annually.
According to the UN, some 32,000 migrants have arrived in Malta and Italy this year.
Nearly 20,000 people perished on the dangerous sea voyage since 1988, according to the Fortress Europe website.