Taoiseach Leo Varadkar hailed the Good Friday Agreement for bringing peace following "decades of bitter violence" during a speech at the United Nations.
Speaking at a US Summit, Mr Varadkar said there is closer co-operation between Northern Ireland and the Republic of Ireland in the 20 years after the historical 1998 agreement was signed.
He told more than 70 heads of state that it brought co-operation in the powersharing Northern Ireland Assembly "at least, most of the time".
In his address to the Nelson Mandela Peace Summit in New York, the Fine Gael leader said: "The Northern Ireland Peace Process was advanced with the wisdom and assistance of friends from around the world, including you, President Ramaphosa.
"For this we will always be grateful."
During his time at the Summit, Mr Varadkar will meet world leaders in a bid to win a seat on the UN Security Council.
Ireland will be competing for one of two seats available for the 2021-22 term with Canada and Norway.
Mr Varadkar arrived in New York on Sunday for the annual UN General Assembly.
Taoiseach @campaignforleo speaks of the powerful legacy of Nelson Mandela & reaffirms that Ireland will continue to uphold Mandela’s commitment to peace, reconciliation & human rights as guiding principles in solving the global challenges of today 🕊️ #UNGA #IrelandUNSC 🇮🇪 pic.twitter.com/xAduPszgET— Irish Foreign Ministry (@dfatirl) September 24, 2018
Speaking on Monday, he said: "With each of you today, I reaffirm that Ireland will continue to uphold the ideals of the United Nations and work with the international community to achieve the aims that Mandela himself worked so tirelessly for during his lifetime.
"In Mandela's story, we recognise the struggles and triumphs of one individual, and the challenges and hope for mankind.
"His fight for freedom and dignity for all - irrespective of race, gender, sexuality, colour or creed - spoke to our vision of our common humanity and proved that the seemingly impossible can indeed become reality.
"It was reflected in South Africa's first democratic constitution, written for a rainbow nation. It is a template for new democracies today."
Mr Varadkar reflected on the legacy of Mr Mandela and recalled how he visited the Irish parliament months after he was released from prison in South Africa in 1990.
Speaking at the UN Mandela Peace Summit to honour his legacy. Mandela’s is a living legacy, entrusted to us so we can be the torch bearers for peace and reconciliation, for this and future generations. #unga #irelandUNSC pic.twitter.com/9uuy5MvR9B— Leo Varadkar (@LeoVaradkar) September 24, 2018
He added: "Twenty-eight years ago, just months after being released from prison, an occasion etched in my memory as a young boy, Nelson Mandela was accorded the special honour of being invited to speak before the Irish parliament.
"There he inspired us with his words as he attacked 'the arrogance of racism' and honoured those who 'dared to cry freedom'.
"I believe the legacy of Nelson Mandela points to a deeper truth.
"A voice may be silenced by death, but its message can never be suppressed. It is heard for all time.
"And it finds a home in the hearts and the minds and the values of those who follow afterwards.
"We should look to the words of this Declaration as we face the challenges of the 21st century.
"And we must give young people a greater say in the decisions that will affect them - the future of our planet.
"War and hatred come in many guises, peace has the same face the world over."
Mr Varakar will hold a series of bilateral discussions with leaders during his time in New York.
PA & Digital Desk