Enhancing communicative competence of healthcare providers (HCPs) is a critical initiative for improving the healthcare experience of sexual and gender minority (SGM) cancer patients. This study presents the development, implementation, and preliminary efficacy of a new training curriculum for improving oncology HCPs’ skills in providing a safe and welcoming environment for SGM cancer patients (SGM Comskil training). Thirty-three (N = 33) oncology HCPs including nurses, nurse leaders, and nurse practitioners participated in a 4.25-hour SGM Comskil Training between July and August 2019. Overall, participants reported highly favorable evaluations of the training, with more than 80% of the participants reacting positively to 12 of the 15 evaluation items assessing engagement and reflectiveness for experiential role-plays with lesbian, gay, bisexual (LGB) and transgender standardized patients (SPs), respectively. Participants also demonstrated significant improvements in SGM healthcare knowledge, self-efficacy, beliefs toward LGB and transgender persons, and SGM-sensitive language use skills following the training. Encouraged by the feasibility of conducting this experiential training with busy cancer care HCPs and the initial favorable participant evaluation of the SGM Comskil training, results clearly indicate that this training can be rolled out into clinical settings to ensure its translational potential. The next steps should assess observable changes in communication skills and SGM-sensitive language skills with SGM patients and improvements in SGM patients’ healthcare experience.