Totnes Police officers said they were "appalled" at the amount of "used and uncapped needles thrown in and around the bushes".
Totnes officers from the Neighbourhood and Response teams attended Vire Island after a report about some drug paraphernalia left in the area on Saturday.
A spokesperson for Totnes Police said: "To say we were appalled at the amount of used and uncapped needles throw in and around the bushes is a massive understatement. This is simply not acceptable not least because some were meters from the children’s climbing frame.
"This behaviour is unacceptable, irresponsible and dangerous.
"With that in mind Officers will be increasing patrols in the area as this is a health hazard and a total disregard for safety."
They asked members of the public to contact them via 101 or the webchat feature on their website if they see "any drug use in the area" or "if it’s happening at the time and there is a risk to anyone please call 999".
The spokesperson concluded: "This will help us protect all who use this beautiful space including children, dogs and nature's little creatures."