Inderjit Singh, sister Harminder Kaur and Sukhdave Basra have run the Lawthorn Farm Restaurant, which is based in a converted steading, under lease since 2007.
However an investment of £420,000 has allowed them to buy the freehold outright.
Some £320,000 of the funding came in a package from Santander Corporate & Commercial, backed by the UK government's Enterprise Finance Guarantee Scheme, with the owners contributing the balance.
Under their stewardship the Lawthorn came third in a House of Commons search for the best South Asian Restaurant in 2009, and enjoys a 4.5 out of 5 rating on Trip Advisor.
Mr Singh, director and chef at Lawthorn Farm, said: "Since we opened the restaurant in 2007 we have steadily grown the business and established its reputation in the area. We are very pleased we have been able to take the opportunity to buy the freehold as this gives us more security over the future of the restaurant."
Santander's Douglas Dunlop said the restaurant is "unique and well known in the Ayrshire area".