Chemsex is understood as 'the intentional use of stimulant drugs to have sex for an extended time among gay, bisexual, and other men who have sex with men'. It is a public health problem because of the increased incidence of cases and because of the consequences on the physical and mental health of those who practice it. Aim: This study aimed to analyze, with the help of the Delphi method, the content validity of a new instrument to assess the risk of behaviors associated with the chemsex phenomenon. Method: First, a bank of items identified from the literature was elaborated. Secondly, 50 experts with knowledge of the chemsex phenomenon at the national level were contacted. A Delphi group was formed with them to carry out two rounds of item evaluation. The linguistic evaluation (comprehension and appropriateness) was assessed using a Likert scale from 1 to 5 for each item. Items that did not reach a mean score of 4 were eliminated. Content assessment was calculated using each item's content validity index (CVI) and Aiken's V (VdA). A minimum CVI and VdA value of 0.6 was established to include the items in the questionnaire. Results: A total of 114 items were identified in the literature. In the first round of Delphi evaluation, 36 experts evaluated the items. A total of 58 items were eliminated for obtaining a CVI or VdA of less than 0.6, leaving 56 items. In a second Delphi round, 30 experts re-evaluated the 56 selected items, where 4 items were eliminated for being similar, and 10 items were also eliminated for not being relevant to the topic even though they had values higher than 0.6, leaving the scale finally composed of 52 items. Conclusion: A questionnaire has been designed to assess the risk of behaviors associated with the chemsex phenomenon. The items that make up the questionnaire have shown adequate content and linguistic validity. The Delphi method proved to be a helpful technique for the proposed objective.