Paul was sworn-in as the state's 14th governor by Justice Lanusungkum Jamir of the Gauhati High Court in a simple ceremony at Raj Bhavan here.
Mizoram Chief Minister Lal Thanhawla, his cabinet members, leaders from various political parties, civil, paramilitary and police officials were present during the ceremony.
Paul, a retired Indian Police Service (IPS) officer and former Police Commissioner of Delhi, was also sworn-in as the governor of Manipur Monday. He was given the additional charge of Manipur.
The Congress-ruled Mizoram has the dubious distinction of having five governors in less than two and a half months.
The successive transfers of the Mizoram governor started with Vakkom B. Purushothaman when he was transferred to Nagaland July 6.
Purushothaman resigned July 11 claiming he was not consulted over his transfer.
Former Gujarat governor Kamla Beniwal was then transferred to Mizoram after Purushothaman was moved to Nagaland as the governor with additional charge of Tripura.
Beniwal, 87, took charge of the office July 9 as the 12th governor of Mizoram. In less than a month, Beniwal was sacked from the post Aug 6.
Former union home secretary Vinod Kumar Duggal, the then incumbent governor of Manipur, was then given the additional charge of Mizoram.
Duggal assumed the office Aug 8 as the 13th governor of Mizoram. He resigned Aug 28.
Maharashtra governor K. Sankaranarayanan was transferred to Mizoram Aug 24 for his remaining term which was scheduled to end in 2017. He resigned immediately after his transfer to Mizoram.
Beniwal, who had a strained relationship with Prime Minister Narendra Modi when he was the Gujarat chief minister, was sacked two months before her tenure was to come to an end.
A Congress leader in Aizawl said the NDA government has chosen Mizoram Raj Bhavan as a "punishment centre or a dumping ground" for governors appointed by the UPA government.
"This approach and mindset would make the constitutional posts 'babyish assignments'," the Congress leader told IANS on condition of anonymity.