The unemployed Syrian man had been living with his family in the Lombardy city of Varese, Italian police said in a statement.
Police said they had evidence that he was planning to join the Syria-based jihadist group, Jabat al Nusra.
Evidence also emerged that he was associated with the planning of prospective terrorist attacks in Italy.
His arrest followed an investigation between authorities in Milan and Genoa, in cooperation with Italy's anti-terrorism squad, Digos.
It comes two days after a 29-year-old man was deported on charges of being an aspiring fighter for the Isis extremist group.
Farook Aftab, a warehouse worker from Pakistan, allegedly planned to carry out an attack on a wine shop in the name of Islam.
Read more: Italy deports Pakistani terror suspect
Italy has deported 35 people on terrorism charges since the start of the year.