Shin was in the US to attend a ceremony marking the completion of a 3.6 trillion-won ($3.1 billion) ethylene plant built by Lotte's chemicals arm in Louisiana.
Lotte Chemical Corp. holds a 88 percent stake in the project, with its US partner, Westlake Chemical Corp., owning the rest.
"Great to welcome Chairman Shin from Lotte Group to the WH," Trump tweeted, together with a photo of himself and Shin's delegation at the Oval Office. "They just invested $3.1 BILLION into Louisiana-biggest investment in US EVER from a South Korean company, & thousands more jobs for Americans."
Referring to South Korea by its official name, the Republic of Korea, he added: "Great partners like ROK know the US economy is running stronger than ever!"
Shin refused to discuss his meeting with Trump when asked by Yonhap, saying only that they talked about "various things."
In a congratulatory message for last week's ceremony, Trump hailed the investment as a victory for both nations and a testament to the strength of their alliance.
He also noted that the plant is one of the biggest investments in the US since the launch of his administration in early 2017.
Lotte Chemical plans to produce 1 million tons of ethylene per year at its Lake Charles, Louisiana, plant, bringing its ethylene production capacity to a total of 4.5 million tons a year.
Ethylene is a core ingredient in the plastics industry. The company said it expects to cut its manufacturing costs by using locally produced shale gas. (Yonhap)