Chop cooked shrimp into bite-sized pieces and add to a large bowl.
Stir in cucumber, tomatoes, red onion, jalapeño, cilantro, salt, and pepper.
Pour lime juice over the mixture and stir to combine.
Cover and refrigerate for 30 minutes to let the flavors meld.
Just before serving, gently fold in the diced avocado.
Serve chilled with tortilla chips or over crisp lettuce.