The ComfortDelGro cab company said driver Sia Ka Tian, 70, discovered the bag in the back of his vehicle after dropping a vacationing couple off at The Sail condominium around 11:30 a.m. Monday, the Straits Times reported Tuesday.
The company said the driver brought the money, which was in a black paper bag, to the ComfortDelGro main office.
"The money is unimportant to me. It doesn't belong to me, so how can I use it?" Sia said.
The money was soon returned to the couple.
"Finding $1 million in cash (U.S. $898,000) is not an everyday affair and, in fact, we wonder how many people would have possibly been tempted by it," ComfortDelGro spokeswoman Tammy Tan said. "We are immensely proud of him, and are glad that the passengers recovered their money."