Justice Karen Grau rejected New Zealand Rugby's bid for an urgent injunction after a two-hour hearing in Wellington's High Court on Friday.
The decision gives the NRL an early win in the dispute over the PNG Chiefs name, though the case is set for a full hearing in a New Zealand court early next year.
New Zealand Rugby went to court before the PNG expansion team's logo and jersey are launched in Port Moresby next week.
It argued that using the name could cause confusion and leave the established Chiefs franchise's brand value "hugely damaged".
The hearing also considered the risk that an injunction could harm the PNG team's efforts to attract players ahead of its debut season in 2028.