The US Treasury said that Senat Shipping was providing "extensive support" to a North Korean company already under sanctions.
It means that any assets the firm holds in the US are frozen and prohibits US citizens from doing business with it.
Senat Shipping has denied the allegations.
The US Treasury makes clear that measures against Senat Shipping also extend to the company's president, Leonard Lai.
It said that Senat Shipping was co-operating with Ocean Maritime Management Company (OMMC), a North Korean firm already under sanctions.
In 2013, a ship operated by OMMC was seized by Panamanian authorities for hiding undeclared military equipment from Cuba under its cargo of sugar.
According to US authorities, Senat arranged the purchase, repair, certification, and crewing of vessels for OMMC.
"Arms shipments transported by OMMC serve as a key resource for North Korea's ongoing proliferation activities," said a US Treasury press release.
The United Nations and the US imposed sanctions on OMMC in July 2014 for the attempted arms import into North Korea.
Senat Shipping's statement confirmed that it had chartered OMMC vessels in the past to operate part of its business but says since then it had stopped dealing with all North Korean ship owners.
The firm denies all of the accusations brought against it by the US.
Company president Leonard Lai said the US move to put him and his company on the blacklist was "purely based on my historical dealings with OMMC and not based on anything illegal".
Under UN sanctions, North Korea is banned from weapons exports and the import of all but small arms. There are also separate US sanctions also target Pyongyang's nuclear arms programme.

After a pregnancy lasting 22 months, Thi Hi Way, a 34-year-old Asian elephant at the zoo, gave birth to the female on Thursday afternoon.
Zookeepers said the calf, which is yet to be named, was on its feet within three minutes and was doing well.
Andy Mckenzie, team manager of elephants at Chester Zoo, described the "very smooth" birth as a "real family occasion".
He said: "They all knew that something was going to happen, especially the older elephants that have seen it all before.
"It was great to see the younger individuals being around the birth and learning from the older cows in the family."
Asian elephants
Source: Chester Zoo

The SPFL has set up a working group to examine the issue of unacceptable conduct.
And it is understood that they would seek financial assistance from the Scottish government.
The facial recognition system was mentioned at a meeting of all 42 clubs on Tuesday.
The debate over the extent to which clubs should be held accountable for the conduct of their followers has been sparked by recent incidents involving Rangers, Celtic and Dundee United supporters.
Hibernian's visit to Ibrox on 28 December was marred by sectarian chants from the home end, while there were complaints of sectarian songs during Celtic's Scottish Cup trip to Stranraer.
Celtic and Dundee United have both condemned their own fans for setting off pyrotechnics.
SPFL board member Mike Mulraney revealed there was not appetite to introduce new strict liability rules.
The Alloa chairman said there is "no chance whatsoever" of clubs agreeing to regulations that could see them punished for the conduct of supporters regardless of whether the club itself is to blame.
A spokesman for the league body said: "The SPFL is working with government and other partners with the aim of establishing a workable solution to help rid our football grounds of unacceptable conduct.
"This work is at an early stage and is not being led by any one club.
"The issue of unacceptable conduct is something that the SPFL, its board and its member clubs are absolutely committed to addressing.
"Recognising that certain behaviours are for society to face and address as a whole, we believe football can take a leading role in moving this issue forward for Scottish society."
The prospect of facial recognition technology has been met with scepticism from the Scottish Football Supporters' Association.
Chairman Simon Barrow said the fans' group is concerned by "a rushed move towards intrusive surveillance".
He added: "There needs to be careful consultation with fans and clubs, alongside wider consideration of how to deal effectively and proportionately with threatening and insulting behaviour.
"The best way forward will involve working with the great majority of supporters who deplore such abuses, rather than making them feel under accusation themselves."
The US has blacklisted a Singapore-based shipping firm over allegations it is supporting illicit arms shipments to North Korea.
[NEXT_CONCEPT]
The birth of an elephant calf has been captured on CCTV at Chester Zoo.
[NEXT_CONCEPT]
The Scottish Professional Football League is considering the use of facial recognition technology at stadiums to help combat anti-social behaviour.