According to the tourist board, this will be the first London agency it has worked with, having recently ended its two-year contract with Jago Communications in Ireland.
During its tenure, the PR firm created campaigns that inspired Irish audiences to visit Scotland, the company said.
VisitScotland continues to work in Ireland, but all of its PR activity is now handled in-house.
"This decision was made so that the UK team can concentrate vital budget and team resource on delivering UK activity with a strong focus on London, which we believe will deliver the largest economic return for Scotland," a VisitScotland spokesperson told PRWeek.
In particular, VisitScotland is looking for an agency with a record of delivering large-scale PR consumer campaigns, experience of creating media cut-through, and an ability to engage with Londoners.
The successful London agency will be expected to promote Scotland as a "must visit, must return" destination, typically targeting consumers that haven't visited Scotland, or else have not been to the country since childhood, the tourist board said.
The contract will run for one year and has a maximum value of £54,000.
Interested agencies are asked to submit proposals via the Public Contracts Scotland website by Friday 27 January.
In the US, VisitScotland works with Laura Davidson PR, which has spent the last 10 years driving tourism from North America to the country.
It has also worked with PR firm Davies Tanner since 2015. The agency handles business events for the tourist board.