Companies will now have to obtain certification for demonstrating equal pay.
Iceland has been ranked the best in the world for gender pay equality for 9 years in a row.
Iceland has made it illegal to pay men more than women.
A new law enforcing equal pay between genders came into effect on January 1, 2018, according to Al Jazeera.
Under the legislation, firms that employ more than 25 people are obliged to obtain a government certificate demonstrating pay equality, or they will face fines.
The law was announced on March 8 on International Women's Day 2017 as part of a drive by the nation to eradicate the gender pay gap by 2022.
Dagny Osk Aradottir Pind, of the Icelandic Women's Rights Association, told Al Jazeera: "The legislation is basically a mechanism that companies and organisations ... evaluate every job that's being done, and then they get a certification after they confirm the process if they are paying men and women equally."
She added: "It's a mechanism to ensure women and men are being paid equally.
"We have had legislation saying that pay should be equal for men and women for decades now but we still have a pay gap."
The Nordic country, home to more than 323,000 people, has been ranked the best in the world for gender equality by the World Economic Forum for nine years in a row.
The Global Gender Gap Report evaluates gender equality in a country using indicators including economic opportunity, political empowerment, and health and survival.
The new legislation was supported by Iceland's centre-right coalition government, as well as the opposition - nearly 50 per cent of the lawmakers in parliament are women.
Ms Aradottir Pind added: "I think that now people are starting to realise that this is a systematic problem that we have to tackle with new methods.
"Women have been talking about this for decades and I really feel that we have managed to raise awareness, and we have managed to get to the point that people realise that the legislation we have had in place is not working, and we need to do something more."
The UK reported a 16.9% pay gap between men and women in 2017.