Private House Stays was founded in 2007 by Archie and Cassie Bouverie, who have run 9B Scotland Street in the New Town as a B&B for more than 12 years.
The website already handles bookings for more than 200 B&Bs, guest houses and boutique hotels.
The VisitScotland website announced last month that it was to close its online booking system, and would instead link to other firms.
Ms Bouverie said: “We are delighted to be working with VisitScotland as one of their booking providers.
“Our online booking form is the friendliest system on the market. Users trying to plan their trip should have fewer boxes to fill in, an unthreatening booking process and a secure contract between the parties.”