The finds included the bowl of a 19th century clay tobacco pipe, a coin from 1918 and a line of old post holes.
The discoveries were made in September as workers began work on the Mediterranean section of the botanic garden, supervised by two archeological advisers.
University of Otago research fellow Chris Jacomb, director of the Southern Pacific Archaeological Research department, said the discoveries were consistent with the theory an old cottage, built in 1865, had once stood on the site.
The post holes were believed to show where the cottage's veranda had once stood, he said.
The holes had been measured and recorded, while the pipe bowl and coin would most likely be offered to the Otago Settlers Museum, although no decision had yet been made, he said.
Dunedin Botanic Garden collections supervisor Barbara Wheeler said the discoveries had not set back the $350,000 project, which was on target to be completed for a formal opening ceremony in February.
The garden was being built on sloping land between the botanic garden's existing rock garden and the upper garden area, with views towards Woodhaugh Gardens.
This week, contractors were building one of five stone walls expected to shape the completed garden.
Work on the stone walls was being carried out by botanic garden staff, who were receiving pointers from Otago Polytechnic landscape tutor Alan Ferguson.
Mr Ferguson said the walls required about 50 tonnes of flat basalt rock sourced from Mt Kettle, near Dunedin, and put together like a jigsaw.
"It's all hand-picked to get the nice flat faces . . . For every one you pick up and put in the wall you probably use about three."
He was enthusiastic about the results, saying the finished project would be "wonderful".
"It's probably about as close as you can get to the whole Mediterranean thing," he said.
The completed terraced garden would include a raised plaza with an ornamental balustrade and pond, and a fountain as its centrepiece.
Plantings, including an olive tree and cedar, would come from coastal and alpine Mediterranean regions including North Africa, Turkey and Lebanon.
The project was partly funded through a substantial bequest to the council by Nancye Sime, a noted chrysanthemum and rose judge who died in 2004, aged 87.
A $40,000 donation from Dunedin couple Dick and Barbara Calvert had also helped, as had fundraising by Friends of the Botanic Garden, including obtaining $100,000 from the Community Trust of Otago.
