David Powell, Charles Breslin, Philip Hill and Garry Jenkins died at the mine in Cilybebyll, near Pontardawe.
The First Minister said:
“The events at Gleision will forever be burned into my memory. None of us can imagine what the families of the men who died went through during the agonising wait for news.
“Those were long hours indeed and when we finally found out their fate, it must have been devastating for the wives, sons and daughters. My sincere condolences go out to the families at what must be a difficult time.
“What happened deep down in that mine at Cilybebyll affected us all, as I said at the time it was a tragedy for all of Wales. The mining industry is burned into the consciousness of Wales; it was a fundamental force in shaping our country.
“However, the human cost that can be extracted along with the coal must never be forgotten. The terrible events a year ago were a grim reminder of the dangers faced by miners every time they walk towards their pit for the start of a shift.
“We were all moved by how the community came together to support the families and we were all impressed by the kindness shown by neighbours at a time of need. I also want to pay tribute to the emergency services who worked tirelessly at great personal risk during those dark hours searching for the miners.
“The tragedy at Gleision must never be forgotten and lessons must be learned to make sure an incident like this doesn’t happen again and such events are consigned to history.”