Objectives Drug use during sex has been associated with sexually transmitted infections (STI). While a growing body of research has investigated drug use during sex among men who have sex with men, data in swingers is limited. Swingers are heterosexual couples who have sex with others and singles who have sex with these couples. Our study assessed the prevalence of drug use during sex and perceived benefits and risks among swingers. Methods In 2018, 1005 swingers completed an online questionnaire that was advertised at Dutch swinger-websites. We assessed the associations between drug use during sex <6 months (any drug use excluding alcohol and erection medicines) and sociodemographic characteristics, alcohol use and condomless sex using backward multivariable logistic regression analysis. We compared drug use, motives, beliefs and experienced effects between heterosexual male, bisexual male and female drug-using swingers using χ2-tests. Results Drug use during sex was reported by 44% (443/1005): 51% in women, 44% in bisexual men and 39% in heterosexual men (P<0.01). Condomless vaginal (46%) and anal sex (22%) was higher in drug-using swingers (vs 34% and 13% in non-drug-using swingers, P<0.001). Among drug-using swingers, XTC (92%), GHB (76%) and laughing gas (69%) were mostly used. Prolonging sex (68%) and increasing arousal (66%) were the most reported motives. Most reported positive effects were feeling happy (78%) and increasing energy (78%). Ninety-four per cent considered drug use to be pleasurable. The most reported negative effect was feeling tired (53%), 7% reported that they might become addicted or felt uncomfortable having sex without drugs. Conclusion This study among a large group of swingers shows that drug use during sex is highly prevalent. STI clinics should discuss drug use during sex among swingers and provide information on safer sex and drug use, while acknowledging the perceived benefits, such as the increased quality of sex.