Souter Investments and JZ International are paying an undisclosed sum to get a 60% shareholding of Winn Group with the Newcastle company's management retaining 40%.
In the 12 months to March 31 this year Winn Group - made up of brands Winns Solicitors, replacement vehicle arm On Hire and treatment division On Medical - had turnover of £40m.
The accident management outsourcing market is changing as recoverable costs for low value claims are now fixed at £500, down from £1200.
Jeff Winn, who set up the business in 2002, said a number of smaller players were exiting the market with consolidation likely.
Mr Winn said the additional investment would be used to help expand its brands around the UK and go after larger contracts.
Confirming the investment meant the group was now valued at £80m he added: "We aim to expand the significantly in the next few years and this gives us the backing to do that.
"It allows us to go after contracts with bigger [insurance] brokers and that could mean hiring 50 to 60 staff in one go if we land one of those."
Souter Investments' managing director Andy Macfie, said: "The accident management sector is undergoing a period of significant change at present and we are confident Winn Group is well placed to grow strongly in this new environment."