"Brad's mother, family and friends are all devastated by his disappearance and we need to find him and bring him home," family spokesman Paul O'Sullivan said yesterday.
"In our best case scenario, we're all hoping Brad's out there and will call us," Mr O'Sullivan said.
Mr Anderson's family is concerned for the 25-year-old's safety after he failed to answer calls or texts to his mobile.
Mr O'Sullivan said the behaviour was "extremely unusual for a guy who is on his phone 24/7".
He was last seen filling his car with fuel at a BP service station on George St on Thursday and his bank account has not been touched since.
"We need help from the public to find out where Brad drove to after he left the service station," Mr O'Sullivan said.
He said Mr Anderson was not the type of person to go away without notice.
"It's very out of character to head off and not contact anybody.
"He is always in contact with people. There is always texting happening and he hasn't made any kind of contact like that at all."
Acting Senior Sergeant Chris George said Mr Anderson was believed to be in the greater Dunedin area, travelling in a distinctive 2000 Nissan Wingroad stationwagon, registration plate EJK998, with "IT Otago" signwriting on its sides.
The University of Otago IT consultant is a European male of thin build, 186cm tall, with blue eyes and short black spikey hair.
He was last seen wearing blue-grey coloured jeans, a light v-neck T-shirt, and a navy blue hooded sweatshirt with red print on it.
Mr O'Sullivan said Mr Anderson's cellphone was transmitting from within a 30km radius of Mt Cargill but had not been used since Thursday.
The family hired a helicopter to search areas with poor cellphone reception on Saturday and teams of people searched the city and outlying areas at the weekend.
His mother travelled from Oamaru to help search and his father travelled from Australia yesterday.
Anyone with any information is urged to contact Dunedin Central police station on 471-4800, or Mr Anderson's family on 021 991180 or 021 11801021.
