Prepare vegetables: Wash and dice the cucumber and cherry tomatoes. Finely chop the red onion and parsley. Place all in a large mixing bowl for easy combining later.
Add chickpeas and tuna: Drain and rinse the chickpeas thoroughly, then add them to the bowl. Flake the drained tuna into small pieces and gently fold it in with the chickpeas and vegetables, making sure not to break up the tuna too much.
Make the dressing: In a small bowl, whisk together olive oil, lemon juice, Dijon mustard, salt, and black pepper until well combined. Taste and adjust seasoning if needed, adding paprika or chili flakes if you like a subtle kick.
Combine salad: Pour the dressing over the chickpea and tuna mixture. Gently toss everything together until all ingredients are evenly coated with the dressing, making sure the flavors meld without mashing the ingredients.
Chill and serve: Let the salad sit for 5–10 minutes to allow the flavors to mingle. Serve chilled or at room temperature, garnished with extra parsley if desired. Perfect as a light lunch, side dish, or picnic option.