Abstract: A handle assembly is to be mounted detachably on one end of a bicycle handlebar and includes a resilient sleeve member that is sleeved on the bicycle handlebar, an integrally formed handle unit that is made of a composite plastic material, and a bolt unit. The integrally formed handle unit has a clamping portion and a handle portion that extends upwardly from the clamping portion. The handle portion has a generally vertical section that extends from the clamping portion, and a generally horizontal section that extends from a distal end of the vertical section. The vertical section of the handle portion is formed with at least one longitudinally extending reinforcing strip that is connected to the clamping portion. The clamping portion has a generally C-shaped section that confines a through-hole and that is sleeved on the first resilient sleeve member.