Edinburgh Castle, Linlithgow Palace, Edinburgh Castle, Kilchurn Castle and Iona Abbey are amongst those to share the investment by Historic Environment Scotland (HES).
Dallas Dhu Distillery in Moray, Fort George fortress near Inverness and Glasgow Cathedral also made the list of 20 properties prioritised by the heritage body.
Three sites which feature in popular television show Outlander have also been included given a surge in visitors to the landmarks.
Blackness Castle in West Lothian, which portrayed Fort William in season one of the show, will be upgraded along with Doune Castle in Perthshire, which was used as the location for Castle Leoch in the series.
Investment will also be made in Craigmillar Castle in Edinburgh, which twinned for Ardsmuir Prison in the time travelling story.
Alex Paterson, chief executive of Historic Environment Scotland, said: “These are ambitious plans which will set new standards for the care of our properties and provide world class visitor attractions with outstanding visitor experiences.
“We’re building on the success of recent years which have seen record numbers of visitors to many of Scotland’s historic sites. We’ve already effectively started our investment programme, with many projects already underway across the country and are in a strong position to deliver on the identified priorities designed to help bring social, economic and environmental benefits for Scotland.”
A total of £12 million will be spent on the properties in 2018/2019 with the spending to be roughly replicated every year until the end of 2021/2022.
The spending is due to enhance the condition of sites and improve the experience of visitors, HES said.
Edinburgh Castle is the top priority for improvement due to, in part, the risk of rock fall from the Castle Rock. As well as managing the deterioration of the volcanic mass, investment will be made to the castle gift shop, audio guides, internal redecoration and stained glass repairs.
Caerlaverock Castle near Dumfries, a 13th Century moated stronghold, is a top 10 priority site for investment. Its visitor experience will be updated for the digital age with the launch of a new augmented reality app that allows visitors to collect a series of virtual animations around the castle and its grounds.
The atmosphere at Doune Castle in Perthshire, which experienced a 42 per cent rise in visitors last year, will be improved with a new lighting system. Visitors will also benefit from a new exhibition on the castle’s history.
Meanwhile, repairs will be made to the main spire at Glasgow Cathedral along with the Black Adder roof and the North Choir stone.
Fiona Hyslop, Cabinet Secretary for Culture, Tourism and External Affairs, said: “During the past two financial years the Scottish Government has committed additional capital funding of around £6 million to support the conservation and management of properties in care.
“I am now pleased to see this plan for investment in our historic environment, and the infrastructure supporting Historic Environment Scotland’s wider visitor offer, which offers such a strong return for our economy, directly generating £528 million in 2017, and supporting an estimated 15,300 full time jobs in Scotland.”