An efficient numerical procedure based on the cubic spline technique is developed to obtain the vertical displacements of the bridge deck using the slope values measured at selected points under the test loading. Most static load tests of bridges are performed to evaluate the stiffness characteristics of bridge structures or to check the accuracy of their computer models. From this standpoint, vertical displacements of the bridge under certain loads have a crucial importance. However, if the bridge is over a river, a lake, muddy ground, or a major highway, conventional displacement transducers cannot be used appropriately for this purpose. Furthermore, strong wind and the bridge’s height badly affect the accuracy of the transducers. Another way to obtain bridge deflection is to use an indirect method. Tiltmeters, which have been increasingly used for construction monitoring and structural testing of bridges, are suitable devices in terms of indirect deflection measurements because of their characteristics such as high sensitivity, easy installation, and small electrical drift. The testing and evaluation procedure developed was applied on a real bridge, and the results indicated that this method could be applied to obtain vertical displacements of bridges as an alternative to the use of conventional displacement transducers.