The Treasury Department did not respond to requests for comment.
Her opposition puts her at odds with the White House, which defended Weiss and other nominees as hard-working individuals [who] will help us tackle the important challenge facing America.
Warren was selected on Thursday for a newly created spot in the Senate Democratic leadership as a strategic policy adviser, a position that will include outreach to liberal groups.
Warren is known for castigating Wall Streets close relationship to many in Washington. She worries that Weisss background only furthers that revolving door, her office said.
She also has concerns about his advisory role on tax inversions, a practice that allows companies to pay fewer taxes by relocating their addresses overseas. Weiss serves as the global head of investment banking at Lazard, a financial advisory firm that is technically headquartered in Bermuda and has worked on tax inversion deals.