This is the 12th installment of the workshop series "MC4BSM", aimed to foster interactions about physics beyond the Standard Model, between model builders, phenomenologists, the authors of relevant tools, and their users in both experiment and theory. Previous workshops have taken place at
MC4BSM 2018 will include a limited number of contributed talks and abstracts. The organizers encourage the submission of abstracts for 15-minute presentations. In selecting the talks to be presented, we will give priority to attendees who are in the early stages of their career.