Background <p>This study aimed to investigate the effect of root dentin pretreatment with different concentrations of chitosan on the push-out bond strength (PBS) of fiber post using a self-adhesive resin cement.</p> Methods <p>After post-space preparation in 56 maxillary central incisors that underwent endodontic treatment and were filled with gutta-percha (Spident, Korea) and AH Plus resin sealer (Dentsply, USA), the teeth were randomly divided into four groups (<i>n</i> = 14) for pretreatment with 2.5% chitosan, 1% chitosan, 17% ethylenediamine tetra-acetic acid (EDTA), and saline. Fiber posts were cemented into the root canals using Panavia SA resin cement. The teeth were then thermocycled (5°C-55°C, 5,000 cycles), and the roots were sectioned into coronal, middle, and apical thirds. The PBS was measured in a universal testing machine. The mode of failure was also determined under a stereomicroscope and a scanning electron microscope (SEM). The PBS data were analyzed using two-way ANOVA and Tukey’s post hoc test.</p> Results <p>The mean PBS of 2.5% chitosan group was significantly higher than that of control group at the coronal, middle, and apical thirds of the root in the post-placement region. However, 2.5% chitosan group had a significant difference in PBS with the EDTA group only in the middle and coronal thirds (<i>P</i> &lt; 0.05). Pretreatment with 1% chitosan and 17% EDTA did not significantly increase the PBS at any level from the root in the post-placement region. Cohesive failure was dominant in 2.5% chitosan group, while mixed failure had the highest frequency in other groups.</p> Conclusion <p>Root dentin pretreatment with 2.5% chitosan improved the PBS of fiber post to root dentin by using a self-adhesive resin cement.</p>