Objectives: In health communication research using video vignettes, it is important to assess viewers' engagement. Engagement scores can indicate ecological validity of the design, and help distinguish between different engagement types. Therefore, we aimed to develop and validate a scale assessing viewers' engagement with video vignettes. Methods: Based on an existing question set, the 15-item, five-dimensional Video Engagement Scale (VES) was developed. The VES was validated in two video-vignettes studies to investigate patient-physician communication. In addition to engagement, we assessed its presumed correlates, e.g., perceived realism of the video and identification with the patient. Results: Internal consistency and test-retest reliability were adequate in both studies (N = 181 and N = 228). Positive correlations between the VES and perceived realism of the video, credibility of and identification with the patient suggested good content validity. Confirmatory factor analysis suggested a four-dimensional model fit, largely resembling our hypothesized model. Conclusions: The VES reliably and validly measures viewers' engagement in health communication research using video vignettes. It can be employed to assess ecological validity of this design. Further testing of the scale is needed to more solidly establish its dimensionality. Practice Implications: We recommend that researchers use the VES, to ensure ecological validity of future video-vignettes studies.