The 13-month-old girl from Barrow, Cumbria, was sexually assaulted by her father before her sudden death in 2012, a judge ruled.
Paul Worthington, 48, was arrested but later told he would face no charges. He denies any wrongdoing.
Senior coroner David Roberts said there was "substantial public interest" in the case. The hearing will take place in Cockermouth on 18 March.
In October 2014, in an inquest lasting just seven minutes, coroner Ian Smith, who has now retired, determined Poppi's death as "unascertained".
In July, two High Court judges agreed to a request from Mr Roberts that a fresh inquest should take place "in the interests of justice".
Mr Roberts said there were "sufficient" reasons for a second inquest.
He said: "The coroner's role is to establish how, when and where Poppi came by her death, where the coroner has reason to suspect she died a violent or unnatural death or where the cause of death is unknown.
"There has been no adequate coronial inquiry to establish the facts.
"The cause of death registered is 'unascertained'. While this may or may not change after evidence is heard at the fresh inquest, it is right that the coroner should examine the medical evidence to endeavour to determine the issue. The family are entitled to this."
Barrow and Furness MP John Woodcock said: "This is an important step in salvaging justice for Poppi Worthington. It is good that the senior coroner decided to conduct a second inquest and recognised the very real public interest in this case.
"There have been too many delays in this investigation already and I hope that this inquest will now proceed as quickly as possible."
The Independent Police Complaints Commission (IPCC) is reviewing how Cumbria Police conducted its investigation into Poppi's death.
But a leaked draft copy of the yet-to-be published IPPC report, which has been seen by the BBC, said the initial police investigation was "not conducted diligently and expediently".
It stated Cumbria's acting chief constable Michelle Skeer took more than a month to hold a meeting over the concerns raised in March 2014 by a High Court family judge who found no "real" investigation was conducted for nine months into the toddler's death.
The IPCC is due to present its final report following the second inquest.
A second inquest is to be held into the death of Poppi Worthington.