The trio are the first marquee names to be announced for the event, which will be played at Saujana Golf and Country Club from February 19-22.
Boasting prize money of $1.21 million, the championship is Asia's richest national Open and will be joint-sanctioned by the Asian PGA Tour and The European Tour for the fifth successive year.
Montgomerie, who won the European Tour Order of Merit title seven years in a row from 1993, and Harrington have enjoyed great success in Asia.
The Scot won the 2003 Macau Open and the TCL Classic in China in 2002, while Harrington hit the headlines when he was triumphant in the joint-sanctioned Omega Hong Kong Open. The Irishman also has a formidable record in the Carlsberg Malaysian Open having finished second twice and fourth once.
Montgomerie will be competing for the first time in the Malaysian Open. He has won 27 times in Europe and played in the Ryder Cup six times, three of which Europe won.
Harrington brilliantly holed a 20-foot birdie putt on the final hole to win the Omega Hong Kong Open. The tournament was the opening event of the European Tour's 2003/2004 season and marked the Irishman's eighth victory on the circuit.
He has been European golf's top performer over recent years and virtually a permanent fixture in the top 10 of the Official World Golf Ranking since arriving there in November 2001, shortly after winning the Volvo Masters in Spain. Last season he finished third on Europe's Order of Merit list, while he was second in 2002 and 2001.
Harrington has not confined his victories to Europe, with America in particular a happy hunting ground. He teamed up with McGinley at Kiawah Island in 1997 to win the World Cup for Ireland for the first time in 39 years, and in 2002 he claimed Target World Challenge in California.
McGinley will always be remembered as the man who holed the winning putt in 2002 Ryder Cup at The De Vere Belfry. His 10-footer on the 18th green secured a half with Jim Furyk and with it the famous trophy for Sam Torrance's team. A three-time winner on The European Tour, McGinley has been a regular visitor to Malaysia during his illustrious career.