The project has doubled the finished product capacity of its Singapore facilities, allowing them to account for about 25% of the company's global chemical output.
The oil major said more than 40 proprietary technologies were unleashed in the plant upgrades.
This includes the deployment of a steam cracker, which processes "an unprecedented range of feedstock, from light gases to crude oil, to produce an expanded slate of premium and commodity petrochemicals".
"Global chemical demand will grow at a faster pace than GDP as people seek higher standards of living and purchase more household and packaged goods manufactured with chemical products," ExxonMobil chairman and CEO Rex Tillerson said at the opening this week.
"Two-thirds of that growth in chemical demand will be here in the Asia-Pacific region.
"ExxonMobil's expanded Singapore chemical plant is uniquely positioned to serve these growth markets - from China to the Indian subcontinent and beyond."
Singapore Economic Development Board chairman Leo Yip said the expansion enhanced Singapore's leadership position as Asia's energy and chemicals hub.
"This latest investment - the single largest manufacturing investment in Singapore's history - is testament to our ability to successfully attract and execute complex mega-projects," he said.