In a statement, the justice ministry said it took the decision to freeze the assets of Taiwanese Tsang Yung-yuan to show the government's resolve to uphold the sanctions issued by the United Nations Security Council against North Korea.
Oil tankers and cargo vessels that were blacklisted are now prohibited from global ports, while businesses are to have their assets frozen.
"The approval of this historic package of sanctions is a clear sign that the worldwide community has been United in efforts to maintain maximum pressure on the North Korean regime", she said.
Despite the diplomatic opening, the United States have made clear they will keep the pressure on Pyongyang to shift course by pressing on with sanctions.
The 21 shipping and trading firms are also subject to a freeze of assets.
The Taiwanese man, Tsang Yung Yuan, is accused of coordinating "North Korean coal exports with a North Korean broker operating in a third country, and he has a history of other sanctions evasion activities", according to the United Nations listing.
Two other companies - Shanghai Dongfeng Shipping and Weihai World Shipping Freight, also based in China - were blacklisted for carrying North Korean coal on their vessels.
The assets of the 21 shipping companies, which include businesses based in the Marshall Islands, Singapore, Panama and Samoa, must now be frozen.
Twelve North Korean firms were blacklisted for running ships involved in illegal transfers of oil and fuel, according to the document.
According to the U.S. Treasury, Tsang had previously coordinated with a Russia-based North Korean broker to help Pyongyang export its coal.
The U.N. Security Council has unanimously boosted sanctions on North Korea since 2006 in a bid to choke off funding for Pyongyang's nuclear and ballistic missile programs, banning exports including coal, iron, lead, textiles and seafood, and capping imports of crude oil and refined petroleum products.
North Korea earned US$200 million in revenue a year ago from exports of coal, iron, steel and other banned commodities, according to a recent report.
North Korean leader Kim Jong Un watches the launch of a Hwasong-12 missile in this undated photo released by North Korea's Korean Central News Agency (KCNA) on September 16, 2017.
Making his first foreign trip since taking power six years ago, leader Kim Jong Un met this week with Chinese President Xi Jinping in Beijing and is due to meet this spring with the USA and South Korean presidents.