Objective Much is unknown about the influence of dispositional optimism and affective communication on genetic counselling outcomes. This study investigated the influence of counselees' optimism on the counselees' risk perception accuracy and anxiety, while taking into account the affective communication during the first consultation for breast cancer genetic counselling. Methods Counselees completed questionnaires measuring optimism, anxiety and the perceived risk that hereditary breast cancer runs in the family before, and anxiety and perceived risk after the first consultation. Consultations were videotaped. The duration of eye contact was measured, and verbal communication was rated using the Roter Interaction Analysis System. Results Less‐optimistic counselees were more anxious post‐visit (β = −.29; p = .00). Counsellors uttered fewer reassuring statements if counselees were more anxious (β = −.84; p = .00) but uttered more reassurance if counselees were less optimistic (β = −.76; p = .01). Counsellors expressed less empathy if counselees perceived their risk as high (β = −1.51; p = .04). An increase in the expression of reassurance was related to less post‐visit anxiety (β = −.35; p = .03). More empathy was related to a greater overestimation of risk (β = .92; p = .01). Conclusions Identification of a lack of optimism as a risk factor for high anxiety levels enables the adaptation of affective communication to improve genetic counselling outcomes. Because reassurance was related to less anxiety, beneficial adaptation is attainable by increasing counsellors' reassurance, if possible. Because of a lack of optimally adapted communication in this study, further research is needed to clarify how to increase counsellors' ability to adapt to counselees. Copyright © 2013 John Wiley & Sons, Ltd.