Assets under management at the group tumbled from $378.1bn at the end of September to $328.5bn by late December.
The US-Australian listed fund group was not immune to the effects of the volatile fourth quarter, which saw net redemptions balloon from $4.3bn in Q3 to $8.4bn in Q4.
Outflows in the final three months of the year accounted for half of the $18bn net redemptions it racked up for the full year. Janus Henderson endured a further $41.2bn hit to assets in the fourth quarter from adverse market and foreign exchange movements.
CEO Dick Weil called the hefty outflows “disappointing” and said the fund group had faced the same global challenges and headwinds as the wider industry last year.
But he added that 2018 had been a year of transformation for the firm which realised $125m in cost synergies ahead of schedule after completing the integration of legacy businesses Janus Capital Group and Henderson Global Investors.
Last August the asset manager dropped its co-chief executive leadership structure, sending former Henderson CEO Andrew Formica out the door with a $12m severance package. Formica has since resurfaced at rival fund group Jupiter and is set to takeover from Maarten Slendebroek as CEO this May.
The group has seen a raft of departures since the merger commenced, most recently losing bond king Bill Gross, who announced his retirement on Monday.
Weil announced the group will spend $200bn on share buybacks this year, double the amount it spent in 2018. The board also approved a quarterly dividend of $0.36 per share.