Two firearms officer tackled the man just after 23:30 last night in the Convent Court area in St Helier.
The Police say he was threatening to harm himself, but he allegedly refused to hand over the knife to officers, after what they describe as a “period of negotiation.”
One of the officers then decided to discharge his taser, “…to prevent (the man) harming both himself and them.”
The man wasn’t injured, and is still in Police custody.
The Police say the incident has already been voluntarily referred to the Jersey Police Complaints Authority.