Lifeguard teams in Port Sagunto, Valencia, sent the drone out to rescue the teen after he got caught in a powerful tide close to the beach earlier this month.
Footage shows the drone flying out to the boy, who is seen struggling and bobbing under crashing waves, and dropping a lifejacket in the water close to him via a wire.
The boy manages to grab the lifejacket and put it on, helping him to float above water until rescue crews reach him.
He was hospitalised after swallowing large amounts of water but he was later discharged.
Sagunto - just north of Valencia - is the first beach in the world to use such drones, run by Valencia-based tech firm General Drones, to support lifeguards.
The drones can fly at 15 metres per second, which is 50km per hour, according to an RTVE report.
They are able to get lifejackets to victims in "record time" and stop them from drowning in those essential first few minutes of a rescue.
Drone pilot for General Drones, Miguel Angel Pedrero, told Reuters: "When we arrived, what we saw was a kid that was already in quite a bad condition with almost no energy to keep floating, so I sent over the lifejacket.
"Because of the heavy waves it was a complicated manoeuvre, but we finally managed to give him the vest and he could float until the lifeguards reached him by jet ski."
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...
"These extra seconds are vital in some cases and also allows the rescue teams to approach the person more calmly and cautiously," Mr Pedrero added.
The boy is one of several people who have been rescued after the local council began trialling them in 2016.
General Drones has more than 30 pilots and drones working across 22 beaches in Valencia and has also launched schemes during several summer seasons along popular holiday destinations on the Costa del Sol and in Benicàssim.