Arrested were Nicholas Rieth, 30, and Alicia DeScalzo, 26, both of Mastic Road.
Police said Rieth was found holding two hypodermic needles. He was charged with endangering the welfare of a child, seventh-degree criminal possession of a controlled substance, possession of a hypodermic instrument and first-degree loitering. DeScalzo was charged with endangering the welfare of a child and first-degree loitering, police said.
DeScalzo is due in court on Tuesday; Rieth on Jan. 28.
Police said the toddler was placed in the custody of Suffolk County Child Protective Services. His condition was not immediately known Monday.