Sign languages are perceived visually and externalized using a signer’s hands, face, and upper body. During sign language comprehension, deaf signers primarily focus their gaze on the face, while hearing non-signers attend more to the hands of a signer. Little is known about whether deaf signers adapt their gaze behaviour when processing unknown signs. Here, we report eye-tracking data from 15 deaf native signers of German Sign Language (DGS) and 15 hearing non-signers who were presented with videos in either DGS or an unknown sign language, all containing no linguistic mouth actions. Our data confirm that deaf signers generally fixate more on the face of a signer than hearing non-signers who attend to the hands in sign space. Moreover, only deaf signers increase their attention to the hands when processing video stimuli consisting of unknown signs compared to familiar signs, suggesting similar adjustment behaviours as observed in spoken languages.