In a large bowl, combine the cubed watermelon, sliced strawberries, diced cucumber, and red onion. Gently toss to mix the ingredients without mashing the fruit.
In a small bowl, whisk together the honey, lime juice, olive oil, salt, and black pepper until well combined.
Drizzle the honey dressing over the fruit and vegetable mixture. Toss gently to coat everything evenly with the dressing.
Add the chopped mint leaves and give the salad a final gentle toss.
Chill the salad in the refrigerator for at least 30 minutes before serving to allow the flavors to meld.