Cook the spaghetti according to package instructions until al dente. Drain and rinse under cold water to cool. Set aside.
In a large mixing bowl, combine the cooked spaghetti, cherry tomatoes, cucumber, bell pepper, black olives, red onion, mozzarella balls, and parsley.
Pour the Italian dressing over the salad and toss gently to combine. Season with salt and pepper to taste.
Cover the salad and refrigerate for at least 30 minutes to allow the flavors to meld.
Before serving, give the salad a good toss and adjust seasoning if necessary.