President Michael D Higgins said he was "truly honoured" to pay tribute and give thanks to the Berkeley community as President and representative of the people of Ireland.
He was speaking at a special reception for first responders at a hotel in Berkeley near the apartment complex where the balcony collapsed killing six young people and seriously injuring seven others.
He said as President of Ireland it was "heartbreaking" to hear of such tragedies, and mentioned the other tragedy in Carrickmines in Dublin when 10 people were killed in a fire.
President Higgins said he had wanted to undertake this journey ever since what he described as "those darkest of days last June" when he had "witnessed from afar" the "invaluable and unwavering support … in times of such anguish and pain".
He said that the tragedy had had an "enormous effect" on the Irish people, and he knew that it had affected the first responders too.
Consul General Philip Grant praised the J1 students who he said were also the "first responders" that night as they were key in providing early care for their friends and helping with identifying who was where.
He said he was immensely proud of the young Irish people.
George and Jackie Donohoe - whose daughter Ashley was one of the young women killed - attended the special ceremony as did their other daughter Amanda.
President Higgins said he wanted to acknowledge their presence and paid tribute to the solidarity and compassion that they had provided to the other families affected in their times of great shared grief.
President Higgins said: "the loss of life and the serious injuries visited on young men and women at the cusp of their adult lives is a tragedy which has moved all of us very deeply. We know that it has affected you also".
He also praised the work of all who worked at the consulate in San Francisco and those who had left and returned when their help was most needed.
He also singled out the volunteers who had provided such assistance to the families of the students who upon arriving in Berkeley "vulnerable and in need of assistance", so many local people, he said "became their pillars of support".
President Higgins added that the people of Ireland were deeply grateful for the practical assistance that had been provided in helping families to arrange for the remains of their loved ones to be brought home.
He said that as a father of four children he was "very conscious" of the tragedy and said he hoped those gathered would accept his "deepest gratitude" for making a dreadful event "more bearable".
He said the connections between Ireland and America were now stronger, saying "our bonds have been made deeper by shared pain and loss".
He will now proceed to the nearby civic park to plant a tree with the Mayor of Berkeley Bates.
Mayor Bates described it as "the worst and most devastating event in the history of the city".
He said that on behalf of all the citizens of Berkeley he was so proud of all the first responders and others who had provided assistance, and he could not thank them deeply enough for doing so.