Almost three million people die each year from work-related causes, the UN agency said.
Its announcement Friday said "The adoption of the inclusion of a safe & healthy working environment in the ILO's framework of fundamental principles & rights at work is an important step to prevent these unacceptable losses."
The "Fundamental Principles and Rights at Work", adopted in 1998, already enshrined the freedom of association and the right to collective bargaining, the elimination of all forms of forced or compulsory labor, the effective abolition of child labor and an end to discrimination in workplaces.
Friday's announcement means they must now also "commit to respect and promote the fundamental right to a safe and healthy working environment, whether or not they have ratified the relevant Conventions," the ILO said on its website.
The new rules will be backed up by a "follow-up procedure" involving annual reports on the progress and obstacles of each country towards the new goal.
he inclusion of health and safety into the fundamental rights has long been sought by trade unions around the world.
The International Trade Union Confederation (ITUC) hailed "the first extension of workers' fundamental human rights in a quarter of a century".
Over three million workers a year die because of their work and tens of millions more suffer injuries and ill health, the ITUC said in a statement.
"This victory, from a sustained three-year campaign by trade unions, professionals and practitioners and victims' families, will begin to turn that deadly tide," it added.