Bring a large pot of salted water to a boil. Add the whole wheat pasta and cook according to package instructions until al dente, typically around 8-10 minutes. Once cooked, drain the pasta in a colander and rinse it under cool water to stop the cooking process and prevent sticking. Set the drained pasta aside to cool completely while you prepare the other ingredients.

In a large mixing bowl, combine the cooled whole wheat pasta, diced cooked chicken breast, finely chopped celery, and halved cherry tomatoes. Gently toss these ingredients together with a spatula until they are evenly distributed.

In a separate medium-sized bowl, whisk together the plain Greek yogurt, Dijon mustard, olive oil, and lemon juice. Season the dressing with salt and pepper to taste, continuing to whisk until you achieve a smooth and creamy consistency.

Pour the prepared dressing over the pasta mixture and toss everything together until the pasta and veggies are thoroughly coated in the creamy dressing.

Give the salad a taste and check the seasoning. If desired, add more salt, pepper, or a splash more lemon juice to brighten the flavors.

For the best flavor, let the salad chill in the refrigerator for at least 30 minutes before serving.