Xargay Casademont walked into the 78th Precinct in Brooklyn on Sunday to tell police about receiving the threat.
The anonymous emailer wrote they wished death on the couple.
The NYPD is in communication with NBA security, which has received other threatening emails from the same sender's address.
An investigation is on going.
The NYPD Hate Crimes Task Force has been also been notified.
Xargay Casademont, 33, and Stewart married in 2021. She reitred in 2021.
Stewart is currently in the middle of the WNBA Finals against the Minnesota Lynx, with the series tied at 1-1.
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