Shape memory alloys (SMA's) are a class of smart materials with the intrinsic properties of shape memory effect (SME) and pseudoelasticity (PE) due to their solid-solid martensitic phase transformations under various thermomechanical loadings. Owing to these features, SMA's have been used in many engineering fields in various forms including spring as actuator elements. To fabricate SMA elements with a desirable shape (e.g. springs, hooks, and Belleville washers) from elementary products (e.g. bars, wires, ribbons, and sheets), specific treatments called "shape setting" are required. Shape setting is accomplished by deforming an SMA specimen to a specified shape, constraining the configuration, and conducting appropriate heat treatments. In this work, SMA helical springs are produced by using two sets of NiTi (Ti-55.87 at. % Ni) wires, one of which showing SME and another showing PE at the ambient temperature. Annealing is performed with the use of a tube furnace under inert atmospheric (Ar). Different pitches as well as annealing temperatures are tried to investigate the effect of such parameters on the thermomechanical characteristics of the fabricated springs. Phase transformation temperatures of the products are measured by differential scanning calorimetry (DSC) and are compared with those of the original wires. Mechanical properties of wires and springs are achieved by tensile and compression tests at different temperatures. Compression tests are also carried out, and stiffness of each spring is determined. The different desired pitches are so that some springs experienced phase transition during loading while the others did not. The former showed a varying stiffness with the applied load, but the latter act as passive springs with a predetermined stiffness. Stiffness and phase transformation temperatures of the made springs are concluded to be influenced by the annealing temperature as well as the adjusted pitches. Also the material parameters for modeling are achieved from the experimental results. In this study, a model is presented to investigate both the SME and PE of the SMA springs. An enhanced one-dimensional constitutive model is assumed to describe the shear stress-strain response within the coils, and equilibrium as well as geometric consistency is utilized to evaluate the axial response of an SMA spring. It is noteworthy that the von Mises yield criterion is used in the extended model one-dimensional model, and the concepts of effective stress and strain were properly employed to derive shear stress-strain response based on a 1-D model for axial loadings. Also, unlike the previous works, neither the Poisson’s ratio is assumed to be 0.5 nor the maximum recoverable shear strain is considered to be equal to the axial one. The numerical results are shown to be in a good agreement with experimental data indicating validity of the proposed approach. The effects of variations in the material parameters on the axial force-displacement response of an SMA spring are further investigated. Key Words Shape Memory Alloy Helical Springs, Shape Setting, Transformation Temperatures, Constitutive Equations, Static Equilibrium Equations