The Ministry of Health said the 48-year-old male foreigner, who is a Singapore permanent resident, had visited Sao Paulo from March 27 to May 7.
He developed a fever and rash from May 10 and was admitted to hospital two days later and isolated, the ministry said in a joint statement with the National Environment Agency (NEA).
Brazil is the hotbed of the mosquito-borne Zika virus outbreak, with the virus blamed for birth defects in babies born to infected women.
"The patient tested positive for Zika on 13 May," the joint statement said, adding the patient would be transferred to the Communicable Diseases Centre at the government-run Tan Tock Seng Hospital.
He would be isolated while undergoing treatment "to minimise the chances of being bitten by mosquitoes and spreading the infection in the community," the statement added.
It described him as "well and recovering" and said he would only be discharged after he tests negative for the virus.
Members of the patient's household are being screened and told to monitor their health and to seek medical treatment when unwell, the statement said.
There is no vaccine or cure for Zika, which in most people causes only mild symptoms - a rash, joint pain or fever.
While the virus is typically spread by mosquitoes, some cases of sexual transmission from infected partners have been detected.