Her son Aidan, who was just 5 months old when she disappeared, will be among those attending.
Ms Furlong's mother, Judith, told the Herald many of her daughter's friends and family "needed" the funeral but she had said her goodbyes a long time ago.
"We've already been through all of this some years ago," she said.
"We had our own little thing. We put camellias in a circle and we planted a tree. I had a little shrine with a candle burning. But I think a lot of other people need this service."
Mrs Furlong will be the only family member to speak at the service.
"I don't really want to, but I have to. I'm trying to write something, but I have to be in the right mood forthat."
She said choosing music was problematic as she was not a fan of the bands her daughter liked.
"We won't be playing any Alice Cooper or Sex Pistols - no thanks.
"But there are a couple of Guns N' Roses songs I can stand. She liked them ... Sweet Child O Mine might be all right, that could possibly be played. But it's mainly a Christian service so I don't know where that will fit in."
Police took Mrs Furlong to the spot where her daughter's body lay for 19 years. Officers were back in the area at the weekend speaking to locals in a bid to generate leads.
Inspector Mark Benefield is leading Operation Darlia, the investigation into Ms Furlong's death, and said he was impressed with the amount of information coming in to police as a result of renewed media coverage about the case.
He said 4200 people had left messages for police on a Facebook page set up to give and collect information about the investigation.
Among them were people offering information about a man named "Tommy", who was mentioned in Ms Furlong's diary. She had planned to spend the night with him around the time she disappeared.
Ms Furlong's funeral will be held at St George's Anglican Church in Epsom on July 20 at 1.30pm. A private cremation will be held afterwards.
CAN YOU HELP?
If you have information on Jane Furlong's death contact police on 0800 675 263, email furlong@police.govt.nz or visit the special "What happened to Jane" Facebook page. Alternatively call Crimestoppers anonymously on 0800 555 111.