She quietly added her mana to many organisations, and her work was recognised when she was appointed a Dame Commander of the British Empire in 1993 after her husband's death. She was awarded the Queen's Service order in the 1986 New Year Honours.
A former minister in Sir Robert's government, John Banks, said Dame Thea was a gracious wife as well as a wonderful homemaker, mother and grandmother.
"She was an ambassador for everything that was good about this country."
Born Thea Dale Flyger, she came from humble beginnings in the Waikato coal mining town of Huntly and, after studying accountancy, she met Robert Muldoon in 1948 through the Junior Nationals.
They married in 1951 and had three children.
"Raised in Huntly, danced at the White House, dined at Buckingham Palace - a pretty good effort," said Mr Banks.
Hawkes Bay community advocate Denis O'Reilly and former Te Puni Kokiri policy manager Harry Tam said they came to pay respects to Dame Thea, with several other colleagues who were in gangs in the 1980s when Sir Robert challenged them to work for the good.