We investigate the influence of the attosecond electron dynamics of photoionization on the femtosecond fragmentation of the molecular ion left behind. We consider the dissociative photoionization dynamics of the N2 molecule, induced by an attosecond extreme-ultraviolet (XUV) pulse in the presence of a moderately strong infrared (IR) laser field. We show that the kinetic energy spectrum of N+ fragments depends on (i) the phases between the different electronic states of N2+ established by the photoionization process and (ii) phases associated with the vibrational dynamics in the dissociating molecular ion. We show that the phase acquired during the photoionization can be obtained from the dependence of the N+ ion kinetic energy release spectra on the time delay between the XUV and IR pulses.