The 27-year-old Scot pulled out of a planned performance at the O2 Arena in London on Thursday, as well as Friday's gig at the Motorpoint Arena in Cardiff.
Nutini - whose third album Caustic Love topped the charts earlier this year - postponed two concerts in Glasgow this week on medical advice.
Fans with tickets should keep them and look out for the rescheduled dates.
A statement announcing the latest postponements said: "Regrettably Paolo Nutini is suffering with severe tonsillitis and is not well enough to perform."
It also offered an apology for the "inconvenience and disappointment" caused.

Police said detectives were investigating the blaze which started shortly before 04:50 GMT on Coniston Road.
The force added the fire is being treated as unexplained and a joint investigation with the fire service has been launched.
Lancashire Fire and Rescue Service said it sent five fire engines to the scene to tackle the blaze.

They have until 20:00 local time (19:00 GMT) on Tuesday to leave the southern part of the sprawling camp.
Anyone remaining will be forcibly removed to allow for the makeshift structures there to be  razed.
The area has become a cultural hub for many of the migrants. It has shops, a school and religious structures.
The authorities said up to 1,000 people could be affected but volunteers on the ground estimated that at least twice that number lived in the area.
Thousands of migrants from the Middle East and Africa have congregated around Calais in the hope of crossing to the UK.
Chart-topping singer Paolo Nutini has postponed a two more UK arena shows due to "severe tonsillitis".
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A person has died in a house fire in Lancaster.
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Hundreds of migrants living in part of a camp in the French port of Calais known as the Jungle have been ordered to leave or face eviction.