Notts secure Philander, Hilfenhaus
Philander, the South Africa seam bowler, will join the club in April and feature in six County Championship matches and three NatWest T20s before he resumes duty with South Africa.
He has previously enjoyed spells at Kent, Middlesex and Somerset, for whom he took 23 wickets at 21.34 in 2012.
Hilfenhaus will take over as overseas player from the NatWest T20 against Leicestershire on June 5. It will be the Australian seamer's first taste of county cricket.
"It is becoming increasingly difficult to recruit an overseas player of high quality to spend an entire season in county cricket so we're very pleased to have two high quality bowlers sharing the spot," Nottinghamshire director of cricket Mick Newell said.
"We made the decision to recruit bowlers because we felt that we needed to add some experience to enable us to take 20 wickets in Championship matches more regularly. Ben and Vernon were keen to have stints in county cricket in 2015 and it's pleasing that they have chosen to join us."
Hilfenhaus, 31 has not played for Australia since 2012 said he has always been keen for a spell in county cricket: "Nottinghamshire is the ideal club for me given their track record of competing for trophies and the proud history of Australians enjoying success there.
"It's hard to find time in the schedule to commit to a full season so sharing the overseas spot with Vernon is ideal for both of us. I've had some good discussions with Mick Newell and Ed Cowan and I'm looking forward to getting started at Trent Bridge."
Philander added: "I've got a lot of cricket to play in the lead-up to my time with Nottinghamshire but I know the job that I have to do and I'll be well prepared for the county season. There is always responsibility to make a personal contribution and hopefully the results will follow and I can help Nottinghamshire make a good start to the season."