In a large bowl mix together the chicken, celery, mayonnaise, onion, tarragon, lemon juice, and zest until the mixture's completely incorporated.
2 cups cooked, cubed rotisserie chicken, 3/4 cup thinly sliced celery, 1/2 cup mayonnaise, 1/4 cup chopped red onion, 1-2 tbsp freshly minced tarragon, 2 tbsp freshly squeezed lemon juice, 1 tsp lemon zest