The announcement came hours after the European Medicines Agency (EMA) said blood clots should be listed as a “very rare” side effect of the vaccine.
IN CHARTS: Who is being vaccinated in Italy?
In the light of that ruling, the US-made jab should be considered “definitely safe,” Italian health authorities said in a statement.
It “should be preferentially administered to people over 60 years old” and those particularly at risk from the virus, they added.
The same guidelines were previously issued in Italy for the Anglo-Swedish AstraZeneca jab, which has also been linked to very rare instances of blood clotting.
Separately, Italy’s coronavirus crisis commissioner said a first consignment of 184,000 J&J doses would be distributed across the country starting Wednesday.
The J&J vaccine is seen as easier to administer and transport than some of its rivals, because it requires just one dose and can be stored at warmer temperatures.
But its introduction in Europe was suspended last week after US health regulators said the shot should be paused over blood clot fears.
Italy and other EU countries are keen to make use of it to accelerate their sluggish vaccination campaigns and bring closer a return to some level of normality in people’s lives.