IG Group did not disclose any further details about the news, nor did it say when Felix would return.
Chief financial officer Charlie Rozes will assume Felix’s day-to-day responsibilities as acting CEO during her absence. Rozes will combine this with his current role.
The financial trading business said this would help provide “continuity” as it executes its strategy.
The news comes ahead of IG Group publishing its 2023 financial year results on 20 July.
In March, IG Group posted a drop in Q3 revenue but did report growth from operations in high potential markets.
Total revenue for the quarter declined by 7% to £239.3m (€278.8m/$303.6m), compared to £257.0m in 2022.
Revenue from core markets fell 18% to £182.6m, which IG Group said reflected lower over-the-counter derivatives revenue in the period.
However, high potential market revenue jumped 60% to £56.7m. IG Group noted strong growth in the US and in Europe with exchange-traded derivatives business.