The Australian pair made the stronger start, breaking early to take the opening set and carrying that momentum into the second as they kept Ostapenko and Arevalo under pressure.
The second seeds steadily found their range, however, raising their level when it mattered most and producing a strong finish to turn the match around and seal their maiden Wimbledon crown.
"I was frustrated after losing my serve in the first set, but I calmed myself down and told myself to keep fighting until the last point. Marcelo was very positive, and that helped us a lot," Ostapenko said.
Arevalo, twice French Open men's doubles champion, became the first Salvadoran to win a Wimbledon title, while Ostapenko added to her Grand Slam resume that includes the 2017 French Open singles title and the 2024 US Open women's doubles trophy.
"Winning this title means a lot. I want to continue to inspire kids in my country that if you put in the effort and believe in your dreams, you can achieve great things in life," Arevalo said.