Li Xiaolin, president of the Chinese People's Association for Friendship with Foreign Countries, said the summit was a shining example of cooperation between LA, Auckland and Guangzhou.
She told of the close links between New Zealand, China and Los Angeles and said she looked forward to welcoming Brown and Garcetti to China, joking about the American's musical talents and Brown's love of sport.
The Guangzhou vice mayor, Wang Dong, was a "rising star, politically", she said.
Wang Dong said he was looking forward to welcoming delegates to Guangzhou for next year's summit. Many city representatives had never been to Auckland before, he said, adding that delegates had come from the city's port and chamber of commerce.
Garcetti praised Auckland for getting 750 registrations for the two-day event and said he hoped businesses were able to bring more jobs to the three cities.
Cities like Auckland, LA and Guangzhou showed massive signs of growth, the LA mayor said.
"Traffic, infrastructure, air quality and housing - we have problems of cities that people want to be in," Garcetti said.
He cited the US company AECOM helping to redesign Auckland International Airport's main terminal as an example of an LA company working in Auckland and Flex Animations producing for Netflix as an example of an Auckland company working in LA.