Background: Although support for family caregivers is an essential component of palliative care, routine provision of such support is often lacking. To improve support for family caregivers, we assessed current practice and influencing factors as perceived by healthcare professionals. Methods: A two-phase study was conducted including a survey exploring healthcare professionals’ practice of supporting family caregivers in Western urbanized Netherlands in 2017, and focus groups exploring facilitators and barriers to supporting family caregivers in 2018. Focus group data were thematically analyzed with deductive coding based on the COM-B system. Results: Of the 379 survey respondents (response 11%), 374 were eligible (physicians, 28%; nurses, 64%; nurse assistants, 9%). The respondents practiced in academic hospitals (52%), general hospitals (31%), nursing homes (11%) and hospices (5%). They reported to always (38%), most of the time (37%), sometimes (21%) or never (5%) provide support to family caregivers during the illness trajectory. Respondents reported to always (28%), sometimes (39%), or never (33%) provide support after death. Four focus group discussions with 22 healthcare professionals elicited motivational facilitators and barriers to supporting family caregivers (e.g., relationship with family caregivers, deriving satisfaction from supporting them), and factors related to capability (e.g., (lacking) conversational skills, knowledge) and opportunity (e.g., (un)availability of protocols and time). Conclusions: Support for family caregivers, especially after the patient’s death, is not systematically integrated in working procedures of healthcare professionals. The barriers and facilitators identified in this study can inform the development of an intervention aiming to enhance support for family caregivers.