Microslot antennas may be provided for electronic devices such as portable electronic devices. The microslot antennas may have dielectric-filled microslots that are formed in a ground plane element. The ground plane element may be formed from part of a conductive device housing. The microslots may be narrow enough that they are not readily noticeable to the naked eye. The microslots may have lengths that allow the microslot antenna to provide antenna coverage in one or more communications bands. A first group of the microslots may be used to provide coverage in a first communications band and a second group of the microslots may be used to provide coverage in a second communications band.