About 100 people congregated outside list MP Michael Woodhouse's Princes St office around lunchtime chanting slogans and waving placards.
Maritime Union of New Zealand communications officer Victor Billot told the Otago Daily Times that "owners and bosses'' stood to benefit and workers would lose under the TPP.
Among its many potential impacts, the TPP could hurt attempts to rejuvenate New Zealand coastal shipping industry, Mr Billot said.
The deal was anti-democratic and exposed New Zealand to litigation from big business interests if governments took actions that did not suit big corporations.
Mr Billot said he was surprised by the turnout in Dunedin yesterday, especially of young people and women.
TPP Action Dunedin spokeswoman Jen Olsen and others were collecting signatures for a Dunedin TPP-free petition, which had more than 300 signatures.
When it had 1000 signatures, the group planned to ask the Dunedin City Council to make the declaration on behalf of the city.
