Healthcare professionals have a key role in promoting physical activity, particularly among populations at greatest risk of poor health due to physical inactivity. This research aimed to develop our understanding of healthcare professionals knowledge, decision making and routine practice of physical activity promotion with older adults. A cross-sectional survey was conducted with practicing healthcare professionals in general practice, physiotherapy, occupational therapy and nursing in Ireland and Northern Ireland. We received 347 eligible responses, with 70.3% of all respondents agreeing that discussing physical activity is their job and 30.0% agreeing that they have received suitable training to initiate conversations with patients about physical activity. Awareness of the content and objectives of national guidelines for physical activity varied considerably across the health professions surveyed. Less than a third of respondents had a clear plan on how to initiate discussions about physical activity in routine practice with older adults. Assessment of physical activity was not routine, neither was signposting to physical activity supports. Considering the COVID-19 pandemic and its implications, 81.6% of all respondents agreed that healthcare professionals can play an increased role in promoting physical activity to older adults as part of routine practice. Appropriate education, training and access to resources are essential for supporting healthcare professionals promotion of physical activity in routine practice. Effective physical activity promotion in healthcare settings has the potential for health benefits at a population level, particularly in older adult populations.