BACKGROUND: Palliative Care Day Services (PCDS) offer supportive care to people with advanced, progressive illness who may be approaching the end of life. Despite the growth of PCDS in recent years, evidence of their costs and effects is scarce. It is important to establish the value of such services so that health and care decision-makers can make evidence-based resource allocation decisions. This study examines and estimates the costs and effects of PCDS with different service configurations in three centres across the UK in England, Scotland and Northern Ireland. METHODS: People who had been referred to PCDS were recruited between June 2017 and September 2018. A pragmatic before-and-after descriptive cohort study design analysed data on costs and outcomes. Data on costs were collected on health and care use in the 4 weeks preceding PCDS attendance using adapted versions of the Client Service Receipt Inventory (CSRI). Outcomes, cost per attendee/day and volunteer contribution to PCDS were also estimated. Outcomes included quality of life (MQOL-E), health status (EQ-5D-5L) and capability wellbeing (ICECAP-SCM). RESULTS: Thirty-eight attendees were recruited and provided data at baseline and 4 weeks (centre 1: n = 8; centre 2: n = 8, centre 3: n = 22). The cost per attendee/day ranged from £121-£190 (excluding volunteer contribution) to £172-£264 (including volunteer contribution) across the three sites. Volunteering constituted between 28 and 38% of the total cost of PCDS provision. There was no significant mean change at 4 week follow-up from baseline for health and care costs (centre 1: £570, centre 2: -£1127, centre 3: £65), or outcomes: MQOL-E (centre 1: - 0.48, centre 2: 0.01, centre 3: 0.24); EQ-5D-5L (centre 1: 0.05, centre 2: 0.03, centre 3: - 0.03) and ICECAP-SCM (centre 1:0.00, centre 2: - 0.01, centre 3: 0.03). Centre costs variation is almost double per attendee when attendance rates are held constant in scenario analysis. CONCLUSIONS: This study highlights the contribution made by volunteers to PCDS provision. There is insufficient evidence on whether outcomes improved, or costs were reduced, in the three different service configurations for PCDS. We suggest how future research may overcome some of the challenges we encountered, to better address questions of cost-effectiveness in PCDS.