The 37-year-old worked with Keed at Ford Performance Racing in 2009, with the engineer then having stints at Brad Jones Racing and DJR Team Penske before spending last year on gardening leave.
"I am so excited to work with Charlie and the team, I met everybody at the end of 2018 and was really impressed with the calibre of people that Charlie has built up over the last few years," Keed said.
"I’ve worked with Frosty before and know what a fantastic driver he is.
"He’s a perfect fit for this team and the new challenge will bring out the best in him for sure.
"The alliance with Triple Eight is another really exciting aspect. We’ve got a lot of work to do but the potential is high.
"It’s hard not to be excited for this year to start."
Holdsworth's 2018 engineer Stuart McDonald and data engineer Nathan Pekolj will work closely with Keed on the entry.