For the first time on the JET tokamak, the polarization of visible synchrotron radiation from disruption-generated runaway electrons (REs) has been measured. This poster presents these data from the JET C38 campaign, specifically from experiments on Runaway Electron Suppression with the Shattered Pellet Injector (M18-36) and Runaway Electron Avoidance and Formation Conditions (M18-37). The polarimeter of the Motional Stark Effect system was used to diagnose the intensity, degree of linear polarization (DOLP), and polarization angle of RE synchrotron emission from over 50 JET pulses. As discussed in [1], this polarization information can give insight into the RE pitch angle distribution as well as the RE current/density profile. For many JET RE plateaus, only vertically-polarized synchrotron radiation is measured, meaning that much of the physics must be extracted from the DOLP. Experimental data are compared with preliminary simulations from the synthetic diagnostic SOFT [2]. [1] RA Tinguely et al 2019 Nuclear Fusion 59 096029 [2] M Hoppe et al 2018 Nuclear Fusion 58 026032