Shares in the country's three telecommunications firms, led by Maxis Communications, extended their Wednesday's rally on the back of strong earnings.
"There is a bit of euphoria after the strong GDP numbers," said a head of sales at a large brokerage. "Good results from Maxis and Telekom also helped."
The main Kuala Lumpur Composite Index finished up 1.36 percent - the best single-day gain since early July - at 818.53 points. Overall volume was a solid 407 million shares worth 852 million ringgit ($224 million). Gainers beat losers by 539 to 189.
Gross domestic product (GDP) in the second quarter grew an unexpectedly strong 8.0 percent from a year earlier, the government said after the market had closed on Wednesday. This was the fastest annual expansion since 2000.
The share market was boosted by gains in phone firms Telekom Malaysia Bhd and Maxis as investors bet that the mobile sector would continue to grow. Close to half of Malaysia's 25 million people carry handphones.
Telekom rose nearly 2 percent to 10.50 ringgit, Maxis gained 2.4 percent to 8.40 ringgit and DiGi.Com added 2.2 percent to 4.70 ringgit.
Maxis said on Wednesday its second-quarter earnings doubled to 462 million ringgit. Telekom reported on Tuesday that its quarterly profit more than tripled.
Leisure-to-power group Genting, which owns Malaysia's sole casino, rose 0.7 percent to 15.0 ringgit after the firm said second-quarter net profit doubled to 224.48 million ringgit on higher visitor arrivals.