Net profit reached 66.2 billion won (US$65.2 million) in the April-June period, compared with a profit of 57.4 billion won a year earlier, the company said in a regulatory filing.
Sales increased 54 per cent to 711 billion won over the cited period, and operating income gained 54 per cent to 29.1 billion won.
Shares of STX Shipbuilding closed at 26,150 won on the Seoul bourse, up 2.55 per cent.
Shipyards in South Korea, the world's largest shipbuilding nation, have enjoyed a heyday in recent years as global shipping lines bet on rising trade led by China.
Soaring oil prices are also increasing demand for offshore drilling structures and oil tankers.