By asset class, equity AUM fell 1.8% for the quarter to $182.8 billion, and fell 6% over the year ended March 31.
Fixed-income AUM increased 0.4% for the three months and dropped 8% for the 12 months ended March 31, to $73.3 billion.
Quantitative equity assets increased 1.65% for the quarter but fell 6% for the year to $48.3 billion.
Multiasset strategy AUM totaled $32.1 billion as of March 31, down 0.3% from Dec. 31 but flat from March 31, 2018.
Alternatives assets fell 22.6% during the quarter and declined 31% over the year to $13.5 billion.
Net income totaled $94.1 million for the quarter, down 11.9% from the previous quarter and down 43% from the year-earlier quarter.
Revenue was $519.3 million in the first quarter, down 4.7% vs. the previous quarter and down 11.6% compared with the last quarter of 2018.
"Overall investment performance for the quarter was strong, but we continue to face pockets of underperformance, which are driving substantial net outflows," Janus Henderson Group CEO Dick Weil said in a news release accompanying the update.
"That said, we are seeing encouraging results in several areas of our business, including momentum in the U.S. retail channel, primarily with our U.S. equity strategies, ongoing growth in our multiasset capability and an improving environment in Continental Europe," he said.