Law enforcement discovered the item after the musician's death on April 5, 1994, but kept its existence private until now. The release, first reported by CBS, comes weeks after the Seattle police department made dozens of never-before-seen photos and reports available to the public.
The note in question appears to mock the Nirvana frontman's marriage vows to Courtney Love.
"Do you Kurt Cobain take Courtney Michelle Love to be your lawful shredded wife even when shes a [expletive] with zits and siphoning all yr money for doping and whoring."
The sentiments are in stark opposition to Cobain's alleged suicide note, in which he refers to Love as a "goddess" and a person "who sweats ambition and empathy."
Cobain and Love married in February 1992, and had one child together, Frances Bean Cobain. The couple's relationship was notoriously troubled, and some fans go so far as to suggest that Love played a sinister role in Cobain's death.
Seattle police officially ruled Cobain's death a suicide, but speculation and questions persist to this day. The 20th anniversary of the singer's death passed earlier this month.