Officers raided two homes in Flowitt Street, Mexborough, on Wednesday and found £300 worth of heroin and cannabis with a street value of £320.
They also seized £500 in cash.
A man, aged 37 and a woman, 39, were arrested and on suspicion of possession of drugs with intent to supply.
They have been released under investigation while enquiries continue.
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Detective Chief Inspector Paul Wilson, crime manager for Doncaster, said: “I want to offer my assurance to our communities in Doncaster that this is just the start of a dedicated, consistent and robust approach to tackling crime and disorder across the borough.
“The local Neighbourhood Policing Team have been carrying out high visibility patrols in the area, and yesterday they also issued four men with summons to appear in court for an incident of violent disorder in Mexborough earlier this year.
“Additional patrols and partnership work will continue to provide reassurance to our communities. We will not tolerate any form of criminality, and I would urge residents to please come forward with any information."