The present paper deals with the qualitative and quantitative structural evaluation and retrofitting of a Reinforced concrete (RC) in-situ bridge deck located in Salavat-Abad Bijar, west of Iran. The bridge has 5 simply-supported spans with two RC girders and a 20-cm solid topping slab in each span. Each span is 20 meters long with the overall width of 8.4 meters. The bridge was constructed over the Ghezel-ozan river in 1979. At present, the bridge shows a high degree of material deterioration with significant structural cracks in the deck beams as well as severe vibration at the times of trucks traffic passing. Visual evaluation suggests that chloride attacks, carbonation reactions, expansion pressure due to rebar steel corrosion and freezing-thawing effects are responsible to the undesirable current condition of the bridge deck. As no documented information regarding the design, construction and maintenance of the bridge are available, a complete reconnaissance program implemented to extract the geometrical as well as material properties of the bridge deck components. Such program includes destructive and non-destructive testing methods. Results of finite element analysis based on the extracted geometrical and mechanical properties of the bridge show significant structural deficiencies in terms of strength and stiffness under the Iranian standard bridge design loads, necessitating urgent retrofitting. Considering technical and economic factors, various retrofitting alternatives have been suggested. Evaluation of those alternative reveals that implementing concrete repair methods using cement-based repair materials along with removing corrosion scales on the rebars and subsequent strengthening with RC jacketing (using self-compacting concrete-SCC) and FRP composite would be the most suitable retrofitting techniques for this bridges. Vibrations would be reduced using new intermediate piers which increases the stiffness and thus the vibration frequency of the bridge decks.