Electronic devices having tilted antenna arrays

An electronic device may be provided with first and second sidewalls, a rear wall, and a display. Multiple antenna panels may be used to convey radio-frequency signals at frequencies greater than 10 GHz. A first antenna panel may radiate through the display while second and third panels radiate through the first and second sidewalls. The second and third panels may be tilted at non-zero angles with respect to the sidewalls. The non-zero angles may be of opposite sign. The non-zero angles may have the same magnitude. The magnitude may be equal to 15 degrees, as one example. Tilting the panels in this way may allow the panels to collectively cover as much of a sphere around the device as possible, including out of coverage areas behind the rear wall caused by conductive material in the rear wall, without requiring additional panels to be disposed within the device.