A mold for forming a joint spacer device or a part thereof includes a rigid container body having a first perimeter profile delimiting a first molding surface configured to shape a first portion of the joint spacer or a part thereof; and a rigid cover provided with a second perimeter profile delimiting a second molding surface configured to shape a second portion of the joint spacer or a part thereof. The rigid container body and the rigid cover are removably engageable to each other, at the first and the second perimeter profile, so as to delimit a cavity corresponding to the external configuration of the joint spacer or the part thereof. The mold includes a weakening system on the rigid container body and on the rigid cover so that they are separable into parts to allow the extraction of a spacer device or a part thereof, molded therebetween.