Minimally invasive percutaneous needle-based procedures such as brachytherapy, ablation, and biopsy are standard clinical procedures in cancer interventions. Active needle steering increases the target placement accuracy, and consequently improves the clinical outcome. In this work, dynamical characteristic analysis and FEM modeling of flexible joints of a 3D steerable active flexible needle, when actuated by three Shape Memory Alloy (SMA) actuators, are studied. The Shape Memory Effect (SME) and Pseudoelasticity (PE) of the SMA actuators, their biocompatibility, and high corrosion resistance have made them appropriate alternatives in biomedical applications. Modelling the dynamics and FEM analyses of the flexible active needle during actuation is essential before predicting the active needle’s behavior inside tissue.