A bicycle handlebar clamp assembly has a handlebar clamp, a fixing nut, and a fixing bolt. The fixing nut includes a threaded bore having a bolt entrance opening and a bolt exit opening. The fixing nut defines a bolt shaft receiving space disposed adjacent the bolt exit opening. The fixing bolt includes a head and a shaft extending from the head. The shaft has a non-threaded portion disposed between two threaded portions. One of threaded portions is disposed closer to the head of the fixing bolt than the other threaded portion. The threaded portions are dimensioned to threadedly engage the threaded bore of the fixing nut. The non-threaded portion has a axial length that is greater than the axial length of the threaded bore of the fixing nut.