Bring a medium saucepan of salted water to a boil. Add the shrimp and cook for about 2-3 minutes or until they turn pink and opaque. Drain the shrimp in a colander and let them cool.
In a large mixing bowl, combine the mixed salad greens, cherry tomatoes, cucumber, red onion, and avocado.
In a separate small bowl, whisk together the olive oil, lemon juice, Dijon mustard, salt, and pepper to make the dressing.
Once the shrimp have cooled, add them to the bowl with the salad ingredients.
Drizzle the dressing over the salad and gently toss until everything is well combined.
Serve immediately, or chill the salad in the refrigerator for 20 minutes before serving for an extra refreshing taste.