The boxes, in which people can deposit illicit substances before being searched - were part of new anti-drug measures considered by city licensing chiefs on Friday.
In a new set of Home Office guidelines last year, the government called for the introduction of such measures.
The contents will be collected and examined by police, who have funding for 20 of the boxes.
Their use in London has helped to recover £18,000-worth of drugs in the past six months.
They have also revealed that clubbers have recently been sold two highly toxic compounds marketed as ecstasy.
Plymouth licensing committee chair Anna Angel, said: "It enables them to get rid of the drugs they have bought, and it also gives us an idea of the sort of drugs that are being sold.
"I think it is quite urgent and I shall be pushing for it."
Other moves include encouraging a strong anti-drugs policy in all clubs, displaying posters with anti-drugs messages, as well as providing free drinking water to clubbers.
The Harbour drugs and alcohol counselling centre in Plymouth already goes into clubs with advice and information.
Tony Pattinson, the centre's outreach manager, said: "It is highly unlikely that young people will put drugs into honesty boxes without getting something in return.
"But if the police were to analyse and test drugs, they could give us feedback about quality and people would know if a certain batch of drugs was contaminated."
~RS~a~RS~International~RS~q~RS~~RS~z~RS~09~RS~)