Economic historian Dr Helen Paul found the hand-written message when she was removing the packing stitches from the kilt, which has been passed down her family over decades.
The message reads: "I hope your kilt will fit you well, & in it you will look a swell. If married never mind. If single drop a line. Wish you bags of luck, & a speedy return back to Blighty."
Underneath was the name of Helen Govan, of 49 Ardgowan Street in Glasgow.
The London Scottish Regiment kilt, manufactured by Peter Wilson of Bridge Street in Glasgow, would have been made for use by a soldier sent to fight in the war, but for reasons unknown, it was never unpacked or worn.
Dr Paul, of Southampton University, is now hoping to find the descendants of the seamstress to uncover the story behind the note.
She said: "This garment has been in our family for a number of decades, and until recently, we were completely unaware there was such an intriguing secret hidden in its folds. It was a real surprise when the note fell out.
"My father tried to trace any relatives of the note's author a few years ago, but his efforts failed and I'm hoping to pick up where he left off.
"It would be fantastic to trace who this lady was."