He said the repeated use of the word "dick" as an insult subjected those with the surname to ridicule, including vulnerable children.
The authority said people with that surname might be more sensitive to its use in general, in broadcasting but found Campbell's reference acceptable.
"Campbell was referring specifically to Donald Trump Jr and most viewers would have interpreted it as meaning 'a stupid or contemptible person' – a widely understood and generally acceptable use of the term," the decision said.
TVNZ responded to the complaint saying: "Breakfast is aimed at adult viewers, it takes a casual and conversational approach to news and current affairs, and its presenters commonly express themselves candidly and with humour, often in colloquial and informal language."
"...children of a vulnerable age are unlikely to watch the news unattended," TVNZ said.
The authority said it was important to consider "freedom of expression" and found it did not cause actual or potential harm.
"There is an established audience expectation that in between news and current affairs segments, there is frequent banter, humour and opinions offered by the hosts.
"Campbell is known for his candid and irreverent remarks.
"The broadcast did not make any mention of people with the surname Dick or actively encourage ridicule of those people," the authority said.
Dick is a common surname of Scottish origin. However, 'dick' is also a common noun with well-established meanings.
