"She was scared out of her wits and is now being cared for in hospital," said Lars Lisberger at Stockholm police.
The jilted ex-husband has been arrested on suspicion of unlawful threats and animal welfare offences.
Knowing that his ex-wife suffered from musophobia - an unreasonable and disproportionate fear of rats and mice - the man arrived at her apartment in the northern Stockholm suburb of Märsta in the early hours of Sunday morning bearing a paper bag full of mice.
The 37-year-old woman awoke to find the scampering murines in her apartment and called the police at 7.30am.
Police arrested the man and took him in for questioning.
The nineteen mice captured at the woman's apartment are also being housed at the police station pending the advice of the county veterinarian.
According to the Aftonbladet newspaper, the man has demanded the return of his mice.
"He has treated both the mice and his ex-wife badly, so I do not think that he should be given any of them. But we shall have to wait and see what the authorities decide," Lars Lisberger told the newspaper.