Jailed Ibrahim Halawa handed his mother a paper bouquet in the colours of the Irish flag to thank the public for the support he has received during his incarceration.
The 20-year-old will mark his birthday in an Egyptian prison today, Tuesday, as his case is heard in court for the 17th time.
Mr Halawa, from Firhouse in Dublin, was detained in a mosque near Ramses Square in Cairo as the Muslim Brotherhood held a "day of rage" over the removal of their elected president Mohamed Morsi in August 2013.
He gave his mother Amina Mostafa the hand-made gift and a letter when they met more than a week ago in the Cairo jail.
"I have made something by my own hands, for so long I have been receiving presents and cards from my amazing family, my great friends and the beautiful kind Irish people," he wrote.
"But on this birthday, I have a present I have made in my cell with memories, a present I have expressed my feelings in. A hand-made flower bouquet with the colours of the Irish flag."
"On my birthday, I want to gift everyone who has always been there for me. I want to gift this to Ireland for raising me to be the man I am today."
Mr Halawa's lawyers have urged Egyptian president Abdel Fattah el-Sisi to act on an application for a decree to secure his release.
A new judge has been appointed to Mr Halawa's case, the fourth put in charge of the trial after he was detained with 493 others on charges that could ultimately see him face the death penalty.
His family claim he has been tortured, suffered electric shocks, beatings, been spat on and moved without their knowledge during his time in custody with several hundred others over the protests.
They appealed for supporters to join a protest at The Spire in Dublin on Tuesday to sign a birthday card and wish him freedom.
"Let us remind Ibrahim that he has not, and will not, be forgotten," his sister Somaia said.
"He always tries to remain strong, especially in front of our mother."
The campaign to free Mr Halawa is also supported by the Reprieve organisation in London, which fights against the death penalty.
Maya Foa, a director at the charity, said: "It's a scandal that Ibrahim Halawa, who was arrested as a child, is spending his 21st birthday caught up in a mass trial where he faces the death penalty along with 493 other people.
"Ibrahim has been through an appalling ordeal at the hands of Egypt's justice system and it is high time that he was released - along with countless other political prisoners and juveniles."
Reprieve called on the Government to urgently renew its calls on the Egyptian president to release Mr Halawa and for the UK the EU to follow suit.