Although women report feeling more pain than men, their pain is often underdiagnosed and undertreated. By proposing a gender-based theoretical conceptualisation, we argue that such sex-related biases may be enhanced or suppressed by contextual variables pertaining to the clinical situation, the perceiver or the patient. Consequently, we aimed to explore the moderator role of two clinically relevant variables in a chronic low-back pain (CLBP) scenario: diagnostic evidence of pathology (EP) and pain behaviours conveying distress. One-hundred and twenty-six female nurses (M = 35.33, SD = 7.64) participated in an experimental between-subjects design, 2 (patient's sex) × 2 (EP: present vs. absent) × 2 (pain behaviours: with vs. without distress). Independent variables were operationalised by vignettes depicting a patient with CLBP. Nurses judged the patient's pain on several dimensions: (1) credibility; (2) disability; (3) severity of the clinical situation; (4) psychological attributions and (5) willingness to offer support. Main findings showed that judgements of women's pain were influenced by EP, while judgements of men's pain were not. Moreover, nurses showed biases against men, but only in the presence of EP. The influence of distress cues was less consistent. Theoretical and practical implications are drawn.