"We should all work together ... To achieve one common goal: protecting people, society and the environment from the harmful effects of ionising radiation that may occur through the inadvertent or malicious use of radioactive sources," Denis Flory said.
Flory was speaking at the opening of a five-day IAEA conference on safety and security around radioactive sources in Abu Dhabi.
Radioactive sources are used in agriculture, industry, medicine and research, mostly in controlled environments, but there are fears that violent groups could try to use them in harmful ways.
These include certain sources used for medical and industrial purposes, the agency says.
"When safely used and regulated, the social and economic benefits from the many applications of radioactive sources are high," the IAEA website says.