Johnston said Porter would have been chuffed at having the dress circle named after her, despite being shy.
"She didn't really like the limelight too much, she'd shy away from that sort of thing," Johnston said.
At the Napier City Council meeting on Tuesday, the council voted for the commemoration.
Porter was born in Napier in 1936, and moved to London aged 22, where she acted in the West End theatre district, including roles in productions of Shakespeare's Merchant of Venice and Twelfth Night.
Her international recognition came from her role as Irene Forsyte in The Forsyte Saga, which was one of the earliest BBC shows to air in the United States and the first to air in the Soviet Union.
She was appointed Officer of the Order of the British Empire (OBE) in 1970.
Despite her achievements, Johnston said Porter was better known overseas than here in New Zealand.
"I think she was probably better known in the UK than she was here," Johnston said.
"I've come across a lot of people in Napier who didn't even realise she was from Napier."
Porter passed away in London in 2001 aged 65, from leukaemia.
She is also being celebrated with an exhibition by MTG Hawke's Bay Tai Ahuriri, which has been running since March this year, and will end in January next year.
Curator of social history at MTG, Gail Pope said people were really enjoying the exhibition.
"Her story has been virtually untold," Pope said.
"She's internationally famous but people don't connect her with Napier at all," Pope said.
Johnston said he and his brother John Porter would like to thank the Napier City Council for the recognition of Porter.
"Like I said, Nyree would be really chuffed."
