There were 88 opioid-related deaths and 74 fatalities as a result of road accidents in 2015, said the PSNI.
Opioid drugs include heroin, morphine, methadone, and prescription drugs such as tramadol and codeine.
Police revealed the figures as they gave an update on Operation Torus, a campaign to tackle street level drug dealing.
Officers have seized more than £309,000 worth of drugs in the first two weeks of the latest campaign.
During Operation Torus, which began on 27 February, police have conducted 244 searches across Northern Ireland, resulting in 59 arrests.
Forty three people have been charged or reported to the Public Prosecution Service.
Announcing the preliminary figures, Det Ch Supt Tim Mairs said drugs remained a "policing priority due to the devastating effects they can cause to individuals, their families and communities".
"The number of deaths in Northern Ireland connected to drug use is on the increase and this is a concern," he said.
"Sadly, these are all preventable."
"A report by the Advisory Council on the Misuse of Drugs in December 2016 highlighted there was an increase of opioid deaths across the UK between 2012 and 2015, with Northern Ireland having the second highest increase of 47% following England at 58%.
"This indicates that, despite the much smaller numbers we are dealing with in Northern Ireland, the rate of increase is worrying."
Police would continue to target drug dealers, he said, but added that the PSNI could not combat the problem without the help of communities and partner agencies.
More people died in 2015 from the misuse of opioid drugs than in road fatalities, the police have said.