Arsenal agree to sign striker Campbell
"Joel Campbell has already shown he is a player with great ability," manager Arsene Wenger told the London club's website on Friday.
"We look forward to the formalities of the transfer being completed."
The 19-year-old has made six full international appearances, scoring twice. He grabbed two goals on his debut in a 5-0 win over Cuba at this year's CONCACAF Gold Cup.
Deportivo have won the Costa Rican Premier League a record 29 times.