Abstract Background The PACE ‘Steps to Success’ programme is a complex educational and development intervention for staff to improve palliative care in long-term care facilities (LTCFs). In a cluster randomized controlled trial, this programme has been implemented in 37 LTCFs in 7 European countries. Alongside an effectiveness study, a process evaluation study was conducted. This paper reports on the results of this process evaluation, of which the aim was to provide a more detailed understanding of the implementation of the PACE Programme across and within countries. Methods The process evaluation followed the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework and involved various measures and tools, including diaries for country trainers, evaluation questionnaires for care staff, attendance lists and interviews (online and face-to-face, individual and in groups) with country trainers, managers, PACE coordinators and other staff members. Based on key elements of the PACE Programme, a priori criteria for a high, medium and low level of the RE-AIM components Reach, Adoption, Implementation and intention to Maintenance were defined. Qualitative data on factors affecting each RE-AIM component gathered in the online discussion groups and interviews were analysed according to the principles of thematic analysis. Results The performance of the PACE Programme on the RE-AIM components was highly variable within and across countries, with a high or medium score for in total 28 (out of 37) LTCFs on Reach, for 26 LTCFs on Adoption, for 35 LTCFs on Implementation and for 34 LTCFs on intention to Maintenance. The factors affecting performance on the different RE-AIM components could be classified into three major categories: (1) the PACE Programme itself and its way of delivery, (2) people working with the PACE Programme and (3) contextual factors. Several country-specific challenges in implementing the PACE Programme were identified. Conclusions The implementation of the PACE Programme was feasible but leaves room for improvement. Our analysis helps to better understand the optimal levels of training and facilitation and provides recommendations to improve implementation in the LTC setting. The results of the process evaluation will be used to further adapt and improve the PACE Programme prior to its further dissemination. Trial registration The PACE study was registered at www.isrctn.com—ISRCTN14741671 (FP7-HEALTH-2013-INNOVATION-1 603111) July 30, 2015.