Lightly grease the inside of the slow cooker or use a liner for easier cleanup.

Spread the sliced kielbasa evenly across the bottom of the slow cooker.

In a bowl, combine chopped apples, brown sugar, apple cider, Dijon mustard, garlic powder, salt, and pepper. Stir until well mixed.

Pour the apple mixture evenly over the kielbasa, coating the slices thoroughly.

Cover and cook on LOW for 3–4 hours or HIGH for 1–2 hours, until heated through and apples are tender.

Stir gently before serving to coat everything in the sauce.

Garnish with fresh parsley if desired and serve warm.