Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente.

Drain the spaghetti in a colander and rinse under cold water to cool.

While the spaghetti is cooking, prepare the vegetables: halve the cherry tomatoes, dice the cucumber and bell pepper, and finely chop the red onion.

In a mixing bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, minced garlic, salt, and black pepper until well combined.

In a large mixing bowl, combine the cooled spaghetti, prepared vegetables, and dressing. Toss gently to combine.

Add the chopped parsley and toss again.

Serve the spaghetti salad chilled or at room temperature.