Seriously ill people near death face difficult decisions about life-sustaining treatments such as cardiopulmonary resuscitation and mechanical ventilation. Patient decision aids may improve alignment between patients' preferences and the care they receive, but the quantity, quality, and routine use of these tools are unknown. We conducted a systematic environmental scan to identify all decision aids for seriously ill people at high risk of death facing choices about life-sustaining treatments, assess their quality, and explore their use in clinical settings. We searched MEDLINE, Google, and mobile application stores and surveyed experts. We included 27 decision aids in our scan. Concerning content, 14 of 27 decision aids for seriously ill people near death were for people with specific diseases and conditions (ie, advanced cancer or kidney disease); 11 concerned individual life-sustaining treatment decisions (ie, cardiopulmonary resuscitation or mechanical ventilation). Only two focused on more general care pathways (ie, life-sustaining intervention, palliative care, and hospice). Twenty-four of 27 decision aids presented options in a balanced way; 23 identified funding sources, and 19 of 27 reported their publication date. Just 11 used plain language. A minority, 11 of 27, listed evidence sources, five documented rigorous evidence-synthesis methods, six disclosed competing interests, and three offered update policies. Preliminary results suggest that few health systems use decision aids in routine patient care. Although many decision aids exist for life-sustaining treatment decisions during serious illness, the tools are deficient in some key quality areas.