Speech therapy is an emerging profession in Vietnam, and there is an estimated 910 000 Vietnamese people who stutter. No research to date has examined Vietnamese speech therapists’ reliability when measuring severity of stuttering in their native language (Vietnamese) and other languages (e.g. English, a common second language). Twenty-five Vietnamese speech therapists rated 20 speech samples (10 Vietnamese, 10 English) of adults who stutter using a 9-point severity rating (SR) scale on two occasions. Approximately half of the judges were able to measure severity of stuttering reliably in Vietnamese. Judges’ performance in English was poorer than in their native language. Irrespective of language, judges showed greater variability of their use of the scale in the moderate range. Results highlight the need for judges to develop intra- and interjudge agreement when using the scale to measure stuttering in their native and other languages. Research into the development and evaluation of practice and/or training packages would be beneficial to this population, in all languages, with a focus in the moderate range of the scale.