The effect of lithium iodide (LiI: 0–85wt%) on the electrochemical behavior of agarose-based polymer electrolytes for dye-sensitized solar cells (DSSC) was investigated. Fourier Transform Infrared Spectroscopy (FTIR) and scanning electronic microscopy (SEM) were employed to characterize the interactions between polymer matrix and salt and the morphology of the agarose electrolytes, respectively. From the AC impedance spectra study, it was determined that the conduction behavior of the agarose-based polymer electrolyte matches the “salt-in-polymer” like behavior of low LiI content (0–25wt%) and “polymer-in-salt” like behavior of high LiI content (25–85wt%). Detailed analysis of characteristic electrochemical processes occurring in DSSC with these agarose electrolytes was also obtained by employing the EIS technique. The impedance spectra showed that the electron lifetime of DSSC was shortened with increasing LiI concentration, while the charge transfer resistance and charge recombination resistance were reduced when LiI concentration was increased.