Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, combine ground chicken, feta, dill, parsley, garlic, breadcrumbs, egg, olive oil, salt, and pepper. Mix gently with hands until just combined, being careful not to overmix.
Roll mixture into 1 1/2-inch balls (about 16-18 meatballs total). Wet hands slightly between rolling to prevent sticking. Place on prepared baking sheet about 1 inch apart.
Bake for 18-22 minutes until meatballs reach internal temperature of 165°F and turn golden brown.
While meatballs bake, combine Greek yogurt, squeezed cucumber, minced garlic, lemon juice, and chopped dill in a medium bowl. Stir until smooth and season with salt to taste.
Let meatballs cool for 2-3 minutes, then serve warm with tzatziki sauce for dipping.
Notes
Ground chicken thighs stay juicier than breast meat, but either works well.
Squeeze cucumber very dry after grating to prevent watery tzatziki sauce.
Do not overmix meatball mixture or they will become dense and tough.
Meatballs can be formed up to 24 hours ahead and refrigerated before baking.
Nutrition
Serving Size:3 meatballs with 3 tablespoons tzatziki