Contractor doubles the value of its original investment and holds on to FM contract at hospital.
Kier received £5.0m for its 25% stake, which is twice the value of the original investment in the project.
Kier Support Services will continue to provide non-clinical facilities management services at the Hospital where it has a 30 year contract which started in 2002.
Kier chief executive John Dodds said: 'This sale demonstrates the value of our PFI portfolio to shareholders which, after disposals, stands at a committed book value of £16m.
'We remain committed to providing facilities management services to the Neath Port Talbot Hospital and to continuing our long term relationship with the Bro Morgannwg NHS Trust'.
SMIF is owned by Star Capital and acquires interests in infrastructure assets from investors in and developers of PFI and PPP assets