The two, father and son, were detained during an early-morning raid in Brescia, police in the northern Italian city said on Saturday.
The suspects managed a money-transfer agency and helped fund the November 26 attacks, police said in a statement.
The day before the attacks, they transferred money to activate an internet phone account that was used by the attackers and their accomplices, Stefano Fonzi, the head of anti-terror police in Brescia, said.
The attacks in India's economic capital killed at least 166 people and left another 300 injured.
Ten men are believed to have carried out the 60-hour assault.
New Delhi and Washington blamed the siege on Lashkar-e-Taiba, a banned Pakistan armed group.
Italian police began the investigation in December after being alerted by the FBI that the money had been sent from Italy, Fonzi told The Associated Press news agency.
The funds were transferred under the identity of another Pakistani man who had never been in Italy and was not involved in the alleged crimes, he said.
The two are accused of aiding and abetting international terrorism as well as illegal financial activity.
Transferring funds using the identity of other people was a common practice at the Brescia agency, Fonzi said in a telephone interview.
Two more Pakistanis were arrested in Saturday's raids for allegedly committing fraud and other crimes using the same system, but they were not linked to the Mumbai attacks.
A fifth Pakistani man escaped arrest and was still being sought.
India has repeatedly called on Islamabad to charge the founder of Lashkar, Hafiz Muhammad Saeed, with masterminding the Mumbai attacks.
New Delhi has been demanding action against Saeed and other Pakistan-based fighters before it will resume a formal peace process.
Pakistani police announced in September that Saeed would be arrested for propagating jihad and collecting funds for a charity he heads.
Mohammed Ajmal Kasab, the sole surviving suspect, told a court in Mumbai in July that he was one of the attackers.
He gave details of his group's journey from Pakistan on a boat, their subsequent landing in Mumbai, and the rampage that followed as they shot and killed people at a railway station, a Jewish centre and two five-star hotels, including the iconic Taj Mahal.