The American, Rebecca Thompson, was found guilty of killing oil worker Mark Lee Thompson in December and sentenced to death on Saturday while her 14-year-old son was given a three-year prison term, said a Western diplomat.
The son's sentence was commuted, the diplomat added, without specifying to what length.
Police said she had confessed in January to hiring two Omanis to kill her husband. The two Omanis, both 17, were jailed to 10 years each.
In a separate case, the court gave a life sentence to German national Dana Gerlich, and four Omanis for killing her father, Gert Manfred Gerlich, in the Omani capital Muscat in December.
The prosecution had alleged that Gerlich, who pleaded not guilty to premeditated murder, decided to have her father killed because he opposed the relationship with her alleged Omani lover.
The father, a 53-year-old car mechanic, was shot in the head at pointblank range in Muscat's up-market Qurum district.