PurposeTo improve shared decision making (SDM) with advanced cancer patients, communication skills training for oncologists is needed. The purpose was to examine the effects of a blended online learning (i.e. e-learning and online training session) for oncologists about SDM in palliative oncological care and to compare this blended format with a more extensive, fully in-person face-to-face training format.MethodsA one-group pre-posttest design was adopted. Before (T0) and after (T2) training, participants conducted simulated consultations (SPAs) and surveys; after the e-learning (T1), an additional survey was filled out. The primary outcome was observed SDM (OPTION12 and 4SDM). Secondary outcomes included observed SDM per stage, SPA duration and decision made as well as oncologists’ self-reported knowledge, clinical behavioural intentions, satisfaction with the communication and evaluation of the training. Additionally, outcomes of the blended learning were compared with those of the face-to-face training cohort. Analyses were conducted in SPSS by linear mixed models.ResultsOncologists (n = 17) showed significantly higher SDM scores after the blended online learning. The individual stages of SDM and the number of times the decision was postponed as well as oncologists’ beliefs about capabilities, knowledge and satisfaction increased after the blended learning. Consultation duration was unchanged. The training was evaluated as satisfactory. When compared with the face-to-face training, the blended learning effects were smaller.ConclusionBlended online SDM training for oncologists was effective. However, the effects were smaller compared to face-to-face training. The availability of different training formats provides opportunities for tailoring training to the wishes and needs of learners.