2025 Platinum
Organisers announced the latest additions to the competition on Monday, with Donald having confirmed his participation in January.
Triple major champion Harrington is up to 47th in the world rankings after finishing joint-ninth at the Phoenix Open on Sunday.
He last appeared in Malaysia in 2006 and ended a two-year victory drought at the elite four-man Grand Slam of Golf event in Bermuda, last October, meaning he'll be keen to notch up another win.
South African Schwartzel, who is 18th in the world rankings, said the Malaysian Open is a great event to be part of.
"It's one of my favourite events of the year and I love Asia - the food, people, culture and golf courses," he told the European Tour website.
The tournament will take place 21-24 March.
© Copyright Press Association
News brought to you by Glenmuir, choose the clothes the pros prefer.
Take a look at our high quality and fashionable golfing accessories