BACKGROUND: Communicating with empathy is an essential skill for healthcare professionals (HCPs). However, current communication training curricula fail to show how empathy communication is done, hindering the effectiveness of this training. This systematic review synthesizes applied linguistic research that shows how empathy is communicated, and what functions empathy communication serves. METHOD: We included research that analysed naturalistic recorded interactions between HCPs and patients in all healthcare settings. We systematically searched five databases for studies published in English up to August 2024. We analysed results and discussion sections of included studies using aggregative thematic synthesis. RESULTS: We identified 1112 studies through systematic searches and included 43 studies in our review. We found eight categories of empathy communication: 1) naming emotions or characterising experiences, 2) sharing similar emotions or experiences, 3) compassionate witnessing and minimal response, 4) claiming or displaying understanding of patients' experiences and emotions, 5) displaying empathy multimodally, 6) response cries, 7) claiming of similar emotions or experiences, and 8) others. Regarding functions of empathy communication, we found four groups: 1) facilitating advice-giving or problem-solving, 2) assisting patients to work with emotions, 3) facilitating patient-centred care, 4) facilitating history-taking activities. CONCLUSION: The reviewed studies provide evidence that empathy communication can be seamlessly incorporated into healthcare consultations. Empathy enhances patient engagement, aids emotional expression, supports problem-solving and helps in situations where patients' and HCPs' views diverge, making it an essential component of healthcare.