Mr Willis is number 12 on the Green Party list and with 87.5% if the vote counted the party was expected to bring 13 MPs to Parliament.
"I don't look at numbers and I always like to wait until the last thing is settled, but everyone tells me that we are there," he said.
"I'll wake up tomorrow and wait for that call, but it is looking very positive . I am expecting to be on a plane tomorrow."
Mr Willis would be one of three MPs elected from Taieri, alongside Ingrid Leary and NZ First's Mark Patterson-- a remarkable result for one seat.
Mr Willis paid tribute to his neighboring Dunedin Green candidate Francisco Hernandez, who he said had made a major contribution to his success.
"He has lifted Dunedin to being the third highest Green polling seat in the country, we have worked very closely in a great combined campaign.""
