"As nuclear technology continues to be widely used, the highest standard of safety must be ensured," he noted, as the first Asian diplomat to head the United Nations nuclear watchdog.
Leading the global body tasked with promoting the safe and peaceful development of nuclear technologies placed him at the forefront of some of the world's greatest challenges.
In the aftermath of the Fukushima Daiichi nuclear plant meltdown in 2011, Amano pushed for tougher safety standards at nuclear plants in Japan. He worked tirelessly toward denuclearizing the Korean peninsula. After IAEA inspectors were kicked out of North Korea in 2009, he created a team that could go back in if a political deal was reached.
He led the work to monitor the global pact with Iran signed by world powers in 2015 to curb Tehran's nuclear development program. Tensions have soared since the US withdrew from the deal one year ago, and Iran has recently inched past the uranium enrichment limits set out in the accord. Despite these setbacks, Amano pressed on.
The US national security adviser said in a statement that Amano's commitment to nuclear nonproliferation and the peaceful development of nuclear energy was unparalleled.
Iran's deputy foreign minister noted in a tweet that he had worked very closely with Amano. He commended the Japanese diplomat for his "professionalism."
UN Secretary-General Antonio Guterres stated in a tweet that Amano's contributions to the peaceful use of nuclear technology and commitment to multilateralism would be remembered by all who had the privilege to know him.
A former colleague pointed out that while many countries might try to manipulate the IAEA, Amano built credibility for the agency by focusing on the facts.
Yasuyoshi Komizo, a former special assistant at the IAEA, recalled some of their times together.
"He made the IAEA very trustworthy by providing the international community with a highly professional level of judgment, facts and reports," said Komizo. "Given the very politically loaded [situations], he provided a solid basis for everyone to make better judgments."
He described Amano as having a very strong sense of responsibility, but also a sense of humor. He said Amano was a Kabuki fan and regularly ducked into the Kabuki theater. He also recalled that Amano owned a classic car and loved to repair it.
In an interview with NHK in April, Amano sent a message to Japan, the only country to have experienced the horrors of nuclear war.
"My hope is that the Japanese people play an active, concrete role in the field of verification, to promote nuclear disarmament and create a peaceful world."
Laying the groundwork for that is Amano's legacy, and his gift to those who continue the struggle.