A bicycle seat clamp assembly is disclosed herein which comprises upper and lower members to provide a vertical clamping force to the rails of a seat to attach a seat to the seat post. The upper and lower members are actuated by a horizontal fastening device which can be tightened or loosened with one hand. The bicycle seat clamp assembly provides for fine tuning of a front to back angular tilt as preferred by the user. Moreover, the seat post can be rotated to the forward direction or the rearward direction to increase a front to back adjustment range of the seat.