The Euro Stars AA-rated manager has taken the decision due to unexpected family circumstances, according to the firm, and is returning to the US.
He will be replaced by Mark Buffett who will take over his fund on October 1.
The announcement of Buffett's appointment marks the second major change on one of Fidelity’s Asian equity portfolios in the past week.
The change on the Japan Advantage fund ends Slattery’s five-year tenure as lead portfolio manager. He replaced Hokeun Chung on the fund in 2007 who had run the Luxembourg-domiciled fund since its launch in 2003.
Fidelity said Buffett is an experienced portfolio manager with a similar style to Slattery. He also has experience of Japanese equities having previously managed the Fidelity Japan Blue Chip fund.
Buffett has been with Fidelity since 1998 and is based in Tokyo.
Commenting on Buffett’s appointment, a spokesperson for Fidelity said: ‘We believe that Marks extensive experience from managing Japanese equities, his investment credentials and strong track record make him very well suited to take over the FF- Japan Advantage Fund.’
Over the past three years the Fidelity Funds – Japan Advantage fund has lost 8.98%. This is while its Citywire benchmark, the Topix TR, fell 17.51%.