Background The National Academy of Medicine recommends that cancer patients be knowledgeable of their prognosis to enable them to make informed treatment decisions, but research suggests few patients receive this information. Objective This qualitative study describes oncologists’ language during discussions of prognosis and treatment goals in clinical interactions with African American patients diagnosed with cancer. Design We analysed transcripts from video recordings of clinical interactions between patients with Stage III or IV cancer (n=26) and their oncologists (n=9). In‐depth discourse analysis was conducted to describe and interpret oncologists’ communication behaviours and common linguistic features in the interactions. Setting and participants Data were from a larger study of patient‐provider communication between African Americans and oncologists at two cancer hospitals in Detroit. Results Prognosis was discussed in 73.1% (n=19) of the interactions; treatment goals were discussed in 92.3% (n=24). However, analysis revealed that oncologists’ description of prognosis was vague (e.g. “prognosis is a bit worse in your case”) and rarely included a survival estimate. Oncologists often used ambiguous terminology, including euphemisms and jargon, and emphasized uncertainty (e.g. “lesions are suspicious for the disease”). Conversation about prognosis was frequently brief, moving quickly to the urgency and details of treatment. Discussion This study demonstrates how oncologists’ language may obscure discussion of prognosis and treatment goals. The identified behaviours may lead to missed opportunities in eliciting and discussing patients’ knowledge about and preferences for their care. Patient‐, provider‐ and system‐oriented interventions are needed to improve clinical communication, especially among minority patients with advanced cancer.