Heat a large saucepan filled with water to a boil. Add broccolini and cook until just bright green, about 1 minute, then immediately drain and place broccolini in an ice bath to stop the cooking and cool.
Chop broccolini into 1-inch pieces. Add to a large bowl.
Add remaining ingredients and gently stir to coat with dressing. Refrigerate, covered, until ready to serve.