Strengthening old bridges is an increasingly relevant strategy for risk prevention and operation continuity in management of infrastructures. Transportation networks are subjected to progressively stricter environmental and load conditions, leading to a growing number of deficient structures, also due to aging and deterioration. However, employable resources are finite, from both economic and environmental points of view. For these reasons, strengthening opportunities should be considered as a viable option, improving bridges with low economic and environmental impact. With this perspective, a selection of some of the most interesting strengthening techniques for old truss steel bridges is presented. To address effective solutions, the most frequent problems in old truss railway bridges are first presented. Literature analysis and experts’ interviews were conducted and compared to results obtained from a representative bridge cluster. Different solutions addressing highlighted problems are then collected and qualitatively evaluated, in terms of efficacy on structural and typical construction requirements. Finally, general remarks and recommendations based on collected evidence are presented.