Police were called to the scene at 3.08pm on Friday, April 4, after the boy is believed to have got into difficulty in the lake.
A search is currently being co-ordinated, and the park has been evacuated to assist emergency crews.
The boy’s next of kin have been informed and are being supported by specialist officers.
A Metropolitan Police spokesperson said: “Police were called at 15:08hrs on Friday, 04 April to Beckenham Place park.
“A 16-year-old boy is believed to have got into difficulty in the water and is now missing.
“Emergency services are currently co-ordinating a search.
“The next of kin has been informed and are currently being supported by specialist officers.
“The park has been evacuated to facilitate the search.”
