This paper describes the design of a Passive Compliant Coupler for Force Control (PCCFC) based on an in-parallel mechanism. The optimal synthesis of the mechanism is performed with the objective of achieving a good quality index. The novel design of the connector (also termed as the leg), a crucial element of the mechanism, is one of the important features of the paper. The shape optimization of connectors of an in-parallel mechanism is obtained by satisfying compliant requirements and considering maximization of signal to noise ratio criteria. The various design aspects of sizing, sensing the displacement, and implementation of the connector are discussed. The in-parallel compliant mechanism for force control is obtained by optimizing the signal to noise ratio at various stages of the mechanism design.