Greenpeace protesters used six tonnes of the dairy sewage to block two main entrances to the Molesworth St offices.
The group said it was protesting over links it believed the government agency had to the Ruataniwha irrigation scheme in Hawke's Bay.
Earlier this year there was some speculation about the fund being a potential investor in the dam, however, ACC has repeatedly refused to confirm or deny its link to the project.
The environmental activists are unhappy about the project, and ACC's alleged links to it, which they believe will result in increased river pollution.
Greenpeace's agriculture campaigner Genevieve Toop said the multi-million dollar project would pollute "our precious rivers".
"And that's just taking the piss," she said. "So we've blockaded ACC's offices in Wellington today with six tonnes of dairy sewage, including cow piss, in large sealed containers.
"Millions of tonnes of pollution ends up in our rivers via cow piss already. And this pollution will only get worse if government departments like ACC throw taxpayers' money at irrigation schemes like Ruataniwha that expand the industrial dairy sector."
She called for the Government to look towards ecological farming methods.
The Ruataniwha water storage project that entailed an 83m-high dam on the upper Makaroro River, and was being driven by the Hawke's Bay Regional Council, has a projected cost of almost $900 million.
