Background Staff may encourage individuals with intellectual disabilities to use manual signs by modelling its use, but implementing key word signing during daily activities can be demanding. Method Staff's use of manual signs was observed in four special schools and four day centres for adults with intellectual disabilities during communicative group activities, non-communicative group activities and mealtimes. Using in situ partial interval coding, we measured staff's communication rate, semantic diversity of manual signs, sign reinforcement and sign imitation. With Chi-squared tests, associations were measured between these variables, the two settings and the three activity types. Results During communicative activities, staff used manual signs significantly more in adult services than special schools. During non-communicative activities and mealtimes, staff seldom used or reinforced signs. Conclusions Staff communicated frequently but did not often model sign use during daily activities. To investigate influence from training background, further detailed measurements are warranted.