Background: The subtle communicative behaviour of individuals with visual and severe/profound intellectual disabilities hinders the success of their interaction with professional caregivers. The bioresponse system, a tool to raise caregivers' awareness of the client's communicative behaviour, may improve the client's joint attention behaviour and the dyad's affective mutuality. Method: Four client–caregiver dyads participated in a randomized multiple baseline study with repeated baseline, intervention and follow‐up observations. The bioresponse system's effect was evaluated with measures of joint attention and affective mutuality. Results: Two clients showed a significant difference on one or two joint attention subscales (including one significant decrease), and for all clients, at least one joint attention subscale revealed a positive trend. Positive trends in affective mutuality scores were observed in two dyads. Conclusions: The results stress the importance of further research to the effects of using the bioresponse system's in daily care for persons with severe/profound intellectual disabilities. [ABSTRACT FROM AUTHOR]