Without significant cooperation between nations and the adoption of new strategies, law enforcement will be left behind, fighting 21st century crime with 19th century tools. Cybercrime has challenged policing capacity in unprecedented ways, demanding increasing cooperation between states, and requiring a more effective investigation capacity. The J-CAT is a Member States led initiative facilitated by Europol’s Cybercrime Center, EC3. This initiative is the first of its kind, born out of frustration with traditional tools available to law enforcement, the J- CAT has illustrated the importance of developing a task force based in a single physical location, governed by a flexible administrative framework, and that elicits the trust of Member States. The J- CAT has prioritised joint investigations on some of the most heinous Internet enabled crimes, including online sexual exploitation of minors, vicious botnets and identity theft rings. The result is an effective platform to collaborate across multiple borders and coordinate international investigations with partners, maximising the effectiveness of international joint and coordinated actions against key cyber threats and top targets. This practitioners’ note outlines the genesis and operations of the J-CAT, identifying key success strategies, lessons learned and opportunities for the future.