Figures from the Office for National Statistics show 11 people died from drug misuse in 2019, down from 26 in 2018. Between 2017-2019, 46 people died.
It comes after Portsmouth City Council’s harm reduction worker - appointed in late 2017 - has worked with hard-to-reach addicts.
More opiates users have been getting treatment in the 12 months to March last year, the city council said.
Meanwhile, Gosport has one of the highest drug-related death rates in Britain when all types of deaths are taken into account.
There were 4,393 drug poisoning deaths in England and Wales – the highest since 1993 and the seventh year in a row with an increase.
Councillor Matthew Winnington, cabinet member for health, wellbeing and social care, said: ‘It's incredibly positive to see the reduction in drug related deaths as this has been an area of focus but clearly our aim would be to have none as every death this way is a tragic loss.
‘We've been successful in increasing the number of residents receiving drug treatment, up seven per cent for opiate users between March 2018 and March 2019. The reduction in drug-related deaths during this period demonstrates the impact of effective treatment programmes.
‘We've also been running overdose prevention workshops for partners and have been continuing to provide Naloxone, the emergency overdose antidote, to vulnerable drug users through a number of pharmacies in the city.
‘The harm reduction worker we appointed in late 2017 has also managed to build relationships with disengaged, hard-to-reach drug users, which is also likely to have played a role in the reduction of drug related deaths.’
Havant saw three misuse deaths last year, down from 11. Gosport had seven, the same as the year before, and Fareham had five, up from three.
Drug misuse deaths include opioids, sedatives, cocaine, other stimulants including caffeine, hallucinogens and psychoactive substances.
Poisonings statistics include drug misuse deaths, and accidental overdoses on medication, intentional self-harm, and criminal poisoning.
Portsmouth saw 20 drug deaths in total, including the 11 from misuse, down from 38 in 2018.
In total Havant had seven, down from 12. Gosport had 10 – the same as previously – and Fareham had nine, up from five.