Exhibit 99.1 Janus Henderson Group plc Reports Third Quarter 2025 Results LONDON — Janus Henderson Group plc (NYSE: JHG; "JHG," "Janus Henderson," or the "Company") published its third quarter 2025 results for the period ended September 30, 2025. Third quarter 2025 operating income was US$172.0 million compared to US$163.8 million in the second quarter 2025 and US$164.7 million in the third quarter 2024. Adjusted operating income, adjusted for one-time, acquisition and transaction related costs, was US$204. ...