New Zealand First leader Winston Peters has visited ACT's offices at Parliament.
Newshub spotted Peters and staffer Darroch Ball heading to ACT's office.
He was there for roughly 15 minutes and then left.
Newshub asked him about how the meeting went but he would not comment specifically.
This is a significant step in coalition talks.
The first contact between New Zealand First and ACT was made on Wednesday with a meeting between ACT chief of staff Andrew Ketels and Ball.
ACT Party leader David Seymour flew to Wellington on Thursday morning after being based in Auckland for most of the week.
Earlier on Thursday, National leader Christopher Luxon told Newshub coalition talks were "progressing well" but he wouldn't give any detail. He also wouldn't say when the first three-way meeting - between National, NZ First and ACT - would happen.
"We don't talk about that. We are just working our way through a process," Luxon said. "It is going well and progressing strongly."
Asked if there would be a Government deal this week, he said: "We won't talk about that.
"We are working hard on it," Luxon added.
Peters also spoke to media earlier on Thursday. He said his party would worked "flat out all day and half the darn night trying to get the matters of the negotiations completed".
"Speed is of the essence. We are not wasting time here.
"Some of us would like to get back home. We have got other things to do. We have been on the trail for two-and-a-half years."
Peters said the coalition negotiations were "substantive [and] progressive".
"It takes a lot of time to get to the detail because the detail has to be cross matched with other details."
