The Central Narcotics Bureau (CNB) seized 1.9kg of heroin, estimated to be worth more than $201,000, in a one-day operation on Thursday.
Three Singaporean men, aged between 40 and 53, were also arrested in the drug bust.
CNB officers were on the lookout for a suspected drug trafficker, who was suspected to be holding on to a large heroin consignment from a syndicate in a neighbouring country.
The suspect, and two other associates, were arrested after being seen travelling in a car in the Marina area. About 965g of heroin was recovered from the car - both wrapped in bundles and stashed under the front passenger floorboard, and loose heroin in the side pocket of the driver's door.
A follow-up raid was conducted at the suspect's hideout in Commonwealth, and another stash of heroin weighing about 950 grams was found hidden in the bedroom. Officers also found drug packing equipment. Investigations are ongoing.
In a statement, CNB said it will "continue to maintain our enforcement efforts against drug offenders in our mission to keep Singapore safe from drugs".