Officers stopped 61 vehicles in Mexborough and found Â£50 worth of cocaine and around Â£1240 worth of cannabis.
They also found that 49 vehicles had illegal red diesel in their fuel tanks.
Two arrests were made for drug offences and a further 20 warning notices were served for traffic-related offences.
The operation was carried out by the Doncaster West Local Policing Team in conjunction with officers from HM Revenue and Customs and the Driver and Vehicle Standards Agency.
The police team tweeted: "Some good results on the traffic operation we have conducted in Mexborough today."