Background: Withholding and withdrawing treatment are deemed ethically equivalent by most Bioethicists, but intensivists often find withdrawing more difficult in practice. This can lead to futile treatment being prolonged. Time-limited trials have been proposed as a way of promoting timely treatment withdrawal whilst giving the patient the greatest chance of recovery. Despite being in UK guidelines, time-limited trials have been infrequently implemented on Intensive Care Units. We will explore the role of time in Intensive Care Unit decision-making and provide a UK perspective on debates surrounding time-limited trials. Methods: This qualitative study recruited 18 participants (nine doctors, nine nurses) from two Intensive Care Units in North West England for in-depth, one-to-one semi-structured interviews. A thematic analysis was performed of the data. Results: Our findings show time is utilised by Intensive Care Unit staff in a variety of ways including managing uncertainty when making decisions about a patient’s prognosis or the reversibility of a disease, constructing relationships with patients’ relatives, communicating difficult messages to patients’ relatives, justifying resource allocation decisions to colleagues, and demonstrating compassion towards patients and their families. Conclusions: Time shifts the balance towards greater certainty in Intensive Care Unit decision-making, by demonstrating futility, and can ease the difficult transition for staff and families from active treatment to palliation. However, this requires clear and open communication, both within the Intensive Care Unit team and with the family, being prioritised when time is used in decision-making.