The duo travelling in a trishaw had been arrested at Bataliya on the Kandy-Colombo road on Sunday.
The Police had found six grams of heroin hidden in the child’s pocket.
The police said that the duo had been in the heroin trade for some time and had used the boy who is related to them when transporting the drugs.
The two suspects had been reportedly arrested while returning to Colombo after distributing heroin to their customers in the Kurunegala area. The police had arrested the suspects while they were trying to sell heroin to another person at Bataliya.
Police are carrying out further investigations.