Using a blender or processor, puree the watermelon and strawberries together.
Juice about ½ of the lime into your mixture. Mix and taste. Add more lime juice if preferred.
Remove leaves off the mint and add to blender. Pulse until mixed. Taste and make adjustments as necessary.
Pour the mixture into your mold, but not quite to the top. Slide in a few slices of strawberries into the sides using a toothpick. Add popsicle sticks and follow your mold's instructions for freezing.
Remove from freezer and run warm water over the top to loosen popsicles from mold.