A method and an apparatus for transmitting broadcast signals thereof are disclosed. The apparatus for transmitting broadcast signals, the apparatus comprises an encoder to encode service data, a frame builder to build at least one signal frame including the encoded service data, wherein a signal frame includes at least one preamble symbol and at least one sub-frame, a frequency interleaver to frequency interleave data in at least one of the preamble and a sub-frame in the at least one signal frame by using a different interleaving sequence generated based on an interleaving sequence and a symbol offset, a modulator to modulate the frequency interleaved data by an OFDM (Orthogonal Frequency Division Multiplex) scheme and a transmitter to transmit the broadcast signals having the modulated data.