Background: Palliative care often requires inter-professional collaboration, offering opportunities to learn from each other. General practitioners often collaborate with specialized palliative home care teams. This study seeks to identify what, how and from whom health care professionals learn during this collaboration. Methods: Cross-sectional survey in Belgium. All palliative home care teams were invited to participate. General practitioners (n = 267) and palliative care nurses (n = 73) filled in questionnaires. Results: General practitioners (GPs) and palliative care nurses learned on all palliative care aspects. Different learning activities were used. Participants learned from all others involved in patient care. The professionals’ discipline influences the content, the way of learning and who learns from whom. Multiple linear regression shows significant but limited association of gender with amount of learning by GPs (M < F; p = 0.042; Adj R2 = 0.07) and nurses (M > F; p = 0.019; Adj R2 = 0.01). Conclusions: This study is the first to reveal what, how and from whom learning occurs during collaboration in palliative care. Training professionals in sharing expertise during practice and in detecting and adequately responding to others’ learning needs, could optimize this way of learning.