We present a detailed, three-dimensional hydrodynamic study of the neutrino-driven winds emerging from the remnant of a neutron star merger. Our simulations are performed with the Newtonian, Eulerian code fish , augmented by a detailed, spectral neutrino leakage scheme that accounts for neutrino absorption. Consistent with earlier two-dimensional studies, a strong baryonic wind is blown out along the original binary rotation axis within 100 ms. From this model, we compute a lower limit on the expelled mass of 3.5 10 –3 M , relevant for heavy element nucleosynthesis. Because of stronger neutrino irradiation, the polar regions show substantially larger electron fractions than those at lower latitudes. The polar ejecta produce interesting r-process contributions from A 80 to about 130, while the more neutron-rich, lower latitude parts produce elements up to the third r-process peak near A 195. We calculate the properties of electromagnetic transients powered by the radioactivity in the wind, in addition to the ‘macronova’ transient stemming from the dynamic ejecta. The polar regions produce ultraviolet/optical transients reaching luminosities up to 10 41 erg s –1 , which peak around 1 d in optical and 0.3 d in bolometric luminosity. The lower latitude regions, due to their contamination with high-opacity heavy elements, produce dimmer and more red signals, peaking after ~2 d in optical and infrared.