Abstract Developments and advances in fabrication technology have led to a new generation of structural shapes, among them, the sinusoidal-web girder. Due to easy execution and potential for structural efficiency, the use of sinusoidal-web girder has been increasing significantly in several segments of civil engineering construction such as bridges, pedestrian walkways, hangars and industrial buildings. In spite of the advantages this type of structural component may offer, there are no design standards or specifications dealing with all the phenomena involved in the behavior of such beams, such as the resistance against lateral-torsional buckling (LTB). As a result, there is a need to develop design recommendations that properly address the flexural capacity of these elements. Following the current trend of semi-probabilistic codes (e.g. load and resistance factor design format), these recommendations shall be developed within the concepts and methods of Structural Reliability. In this paper, reliability-based design recommendations for sinusoidal-web beams for the limit state of LTB are presented. To this end: (i) an experimental investigation on the resistance of sinusoidal-web beams has been performed, (ii) a finite-element model has been developed and validated by experimental results, (iii) a theoretical model for the sinusoidal-web beam resistance prediction is proposed, (iv) a comprehensive program was established toward the assessment of both physical and epistemic uncertainties related to the basic variables, (v) reliability analyses are performed using First Order Reliability Method (FORM), and (vi) resulting implicit reliability levels are checked against current practice. It is shown that the implicit safety levels in the proposed recommendations are in agreement with current trends in structural engineering practice.