Video-polysomnography (v-PSG) is essential for diagnosing rapid eye movement (REM) sleep behavior disorder (RBD). Although there are current American Academy of Sleep Medicine standards to diagnose RBD, several aspects need to be addressed to achieve harmonization across sleep centers. Prodromal RBD is a stage in which symptoms and signs of evolving RBD are present, but do not yet meet established diagnostic criteria for RBD. However, the boundary between prodromal and definite RBD is still unclear. As a common effort of the Neurophysiology Working Group of the International RBD Study Group, this manuscript addresses the need for comprehensive and unambiguous v-PSG recommendations to diagnose RBD and identify prodromal RBD. These include: (1) standardized v-PSG technical settings; (2) specific considerations for REM sleep scoring; (3) harmonized methods for scoring REM sleep without atonia; (4) consistent methods to analyze video and audio recorded during v-PSGs and to classify movements and vocalizations; (5) clear v-PSG guidelines to diagnose RBD and identify prodromal RBD. Each section follows a common template: The current recommendations and methods are presented, their limitations are outlined, and new recommendations are described. Finally, future directions are presented. These v-PSG recommendations are intended for both practicing clinicians and researchers. Classification and quantification of motor events, RBD episodes, and vocalizations are however intended for research purposes only. These v-PSG guidelines will allow collection of homogeneous data, providing objective v-PSG measures and making future harmonized multicentric studies and clinical trials possible. Statement of Significance Rapid eye movement (REM) sleep behavior disorder (RBD) has gained increasingly relevance, as its isolated form (isolated RBD) is an earlystage alpha-synucleinopathy. Moreover, a prodromal RBD phase has been described. A definite identification of these conditions requires video-polysomnography (v-PSG). Despite the existence of international v-PSG diagnostic standards for RBD, some particular aspects are not addressed or subject to interpretation. Additionally, prodromal RBD is still not clearly defined. For these reasons, different centers apply slightly different methods. To allow future harmonized multicentric studies and clinical trials, unambiguous v-PSG guidelines by the Neurophysiology Working Group of the International RBD Study Group are provided here. These guidelines will allow harmonization of diagnostic methods and enable a significant research advancement in the field of RBD and its prodromal phase.