A hydraulic brake lever apparatus is provided with a brake lever housing, a piston, a mounting structure, a brake lever, a fluid reservoir and a diaphragm. The brake lever housing includes a cylinder having the piston movably disposed within the cylinder. The mounting structure mounts the brake lever housing to a bicycle handlebar. The brake lever pivots relative to the brake lever housing to move the piston within the cylinder. The fluid reservoir fluidly communicates hydraulic fluid with the cylinder via a port. The fluid reservoir has a cylindrical shape and lies in a side by side relationship with the cylinder. The diaphragm is disposed within the fluid reservoir, and includes a substantial arrowhead shaped portion that allows the volume of the diaphragm to change smoothly while ensuring the volume of the hydraulic fluid chamber within the fluid reservoir.