Rugby fans across the world were shocked to hear of the death of the New Zealand winger last week at the age of 40, after he suddenly collapsed hours after returning from a trip to Dubai.
New Zealand prime minister John Key announced on Monday that the service, at the city's Eden Park stadium, would be open to all. A private funeral for the All Blacks favourite takes place the following day.
Key wrote on his official website: "Jonah touched people's lives across the country and around the world.
Lomu's family touched by tributes to legendary winger
"This service will be open to all members of the public who want to remember the significant contribution Jonah made, not only to rugby here and overseas, but also to the wider community through his work with charities such as UNICEF and Kidney Kids NZ.
"The service will be a celebration of Jonah's life and I expect a large number of people will want to be there."
In addition, an event is planned for Saturday at Auckland's Vodafone Events Centre, allowing Pacific Islanders to pay their respects in their traditional way.
Lomu, born in Auckland to Tongan parents, had suffered from health problems since his retirement from the game in 2002 due to a rare kidney disease.
Tributes pour in for Jonah Lomu: 'A freak, a nightmare and the nicest, nicest guy'