The Black Watch Museum is the first location in mainland Scotland to host Weeping Window by artist Paul Cummins and designer Tom Piper,
By the end of WW1, almost 9,000 Black Watch soldiers were killed and almost 20,000 wounded.
The sculpture flows from the castle's second floor turret window.
It has been installed as part of the UK-wide tour of the poppies by 14-18 NOW, the arts programme for the World War One centenary.
The exhibition runs at the museum in Balhousie Castle until 25 September.
The Black Watch Museum chief executive, Anne Kinnes, said: "We are honoured to have been chosen to host this commemorative sculpture here at the home of the Black Watch.
"We hope that over the next 12 weeks we will welcome many visitors who will be able to reflect and remember those who made the ultimate sacrifice and those many individuals who are still today affected by conflict."
Nigel Hinds, executive producer of 14-18 NOW, said: "Telling the story of Scotland's premier Highland regiment, the Black Watch castle and museum is a poignant and fitting place for the poppy sculpture Weeping Window to be presented as part of its tour of the UK.
"The poppies have an incredible ability to bring generations together to share stories of the First World War."
Weeping Window is one of two sculptures taken from the installation Blood Swept Lands and Seas of Red, which was displayed at the Tower of London in 2014.
The installation featured 888,246 poppies, one to honour every death in the British and colonial forces of World War One.
A sculpture featuring thousands of handmade ceramic poppies commemorating those who died in World War One has opened in Perth.