The emergence of the video abstract as a new digital genre of science communication has allowed researchers to increase their visibility and engage with larger audiences by employing a complex interplay of different semiotic modes. This paper studies strategies and multimodal resources for building credibility in a small corpus of 16 video abstracts on mathematics published online in the Journal of Number Theory (Elsevier). By adopting a multimodal discourse analysis (Kress, 2010) perspective and drawing on previous research on video abstracts (e.g., Coccetta, 2021;Liu, 2019Liu, , 2021 and persuasion in digital academic genres (e.g., Luzón, 2019;Valeiras-Jurado, 2020), this study explores persuasive strategies for enhancing credibility and the semiotic resources used for their realisation. The analysis considers six persuasive strategies (attention-getting, constructing an authorial persona, engagement, framing, logical reasoning and providing proof) while exploring how the written and spoken verbal modes interact with mathematical symbolism and non-verbal visuals. The results suggest that persuasive strategies used for building credibility vary across different types of video abstracts and differ from those used in printed abstracts.