In civil engineering the durability assessment models are not frequently applied to various stages of the life cycle of reinforced concrete (RC) structures. During the design phase, existing models, using deterministic or probabilistic approaches, assist in defining the quantified requirements for RC structures or members to achieve the desired performance level. Durability assessment is critical not only during the design phase but also during the service phase (for instance, maintenance planning). This research is focused on developing a probabilistic model for predicting the remaining service life of RC beams strengthened with CFRP tape under operational load based on structural reliability. The proposed model was tested based on data from existing theoretical and experimental studies of RC beams strengthened under load. Based on the achieved reliability levels (reliability indexes and failure probabilities of beams after strengthening were obtained in the study), recommendations are provided for predicting the corresponding remaining service life of the members. The impact of the input random parameters of the model on the obtained reliability results and remaining service life has been evaluated. An analysis of the indicators obtained based on existing standards and the potential for their use in the context of strengthened RC structures was conducted.