Democratic Senator Richard Blumenthal said Wilbur Ross's failure to disclose this information was "inexcusable".
The Paradise Papers show he retained an interest in a company shipping oil and gas for a Russian energy firm, Sibur.
Two of Sibur's owners are subject to some form of US sanctions.
The US commerce department says Mr Ross has not done anything illegal and never met any of the figures under sanctions.
The revelations come as part of a huge leak of financial documents revealing how the powerful and ultra-wealthy, including the Queen's private estate, secretly invest vast amounts of cash in offshore tax havens.
What did Wilbur Ross do, according to the leaks?
The leaks show he has investments in Navigator Holdings, which earns millions a year transporting oil and gas for Sibur. Two major Sibur shareholders have been sanctioned by the US:
Russian billionaire Gennady Timchenko, who has at least 12 companies connected to him
The Russian natural gas company, Novatek, belonging to Leonid Mikhelson
Another key Sibur shareholder is President Vladimir Putin's son-in-law, Kirill Shamalov, who holds a 3.9% stake in the firm. While he is not subject to sanctions, his father, Nikolai, is.
A commerce department spokesman did not dispute the revelations.
"Secretary Ross recuses himself from any matters focused on transoceanic shipping vessels. Panorama, adding that the secretary worked "closely with Commerce Department ethics officials to ensure the highest ethical standards".
The US imposed some sanctions after Russia annexed Crimea in 2014. Others were imposed last year for alleged interference in the US presidential election.
The commerce department said Mr Ross had "been generally supportive of the administration's sanctions of Russian and other entities".
What's the problem then?
Prior to being confirmed in office as treasury secretary, Wilbur Ross did not reveal to Congress the full details of his company holdings.
According to the leaks, he retains a financial interest in Navigator Holdings via a number of companies in the Cayman Islands, some of which he did disclose at the time of his confirmation.
However, under the disclosure rules he did not have to declare his interest in Navigator Holdings.
But questions will be raised about Mr Ross's potential conflicts of interest and whether his ties undermine US sanctions against Russia.
"Our committee was misled, the American people were misled by the concealment of those companies," Democratic Senator Richard Blumenthal told NBC News after the revelations came to light.
Mr Blumenthal has called for an investigation into the treasury secretary's links to President Putin's son-in-law.
The leaks come as an investigation led by special counsel Robert Mueller into Russian connections to Donald Trump's 2016 campaign team continues.
Mr Trump's presidency has been dogged by allegations that Russians colluded to try to influence the outcome of the election. He has called the allegations "fake news".
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