Synchrotron emission from relativistic jets can be highly polarized. I demonstrate that the polarimetric signature of jets in X-ray binaries is detected in the infrared and is highly variable. This reveals the turbulent magnetic geometry in the compact jet. I present the first ever test for a correlation between optical polarization and X-ray flux of an XB (Sco X-1, 50 years after its discovery), using simultaneous data with sub-second time resolution. In two XBs, the evolution of their broadband spectra suggests synchrotron emission from the jet likely dominated both the infrared and X-ray flux during their hard state outburst decays. From these results, we predict that high, variable levels of X-ray polarization from XB jets will be detected by future spaceborne X-ray polarimeters.