Owing to the trend toward minimally invasive surgery, manipulators are in demand to achieve more accessibility, agility, and miniaturization. However, conventional manipulators are not flexible, miniaturized, or strong enough to perform surgical procedures in deep, confined spaces. Moreover, the continuum manipulator has additional problems caused by redundancy, such as shape-distortion, deflection, and wire overtension problems occurring during payload handling. To overcome these problems, a novel constrained continuum (CC) manipulator is proposed. The CC constrains the redundancy mechanically by using auxiliary links attached to the main continuum links. Its main advantage consists of significantly enhancing the payload capability by the constraining mechanism and the increased length of the moment arm. The proposed manipulator was verified as capable of repeatedly handling a payload of up to 300 g without exceeding the expected trajectory. Two types of in vivo animal trials demonstrated the manipulators performance regarding maneuverability, workspace, and payload, to successfully resect the tissue. This paper presents the kinematic/mechanical analysis results and proposes the optimization of the key parameters and foundational guidelines for the CC joint. We believe that the proposed manipulator advances the field of surgical robotics owing to its ability to overcome surgical procedures at a standstill.