Social media influencers (SMI) are individuals with large follower engagement, who can shape the thoughts and dietary behaviours of their audience. Concerns exist surrounding the spread of dietary misinformation by SMI, which may impact negatively on public health, yet no standards currently exist to assess the credibility of their information. This study aimed to evaluate the credibility of key SMI weight management (WM) blogs (n = 9), piloting a pre-prepared credibility checklist. SMI were included if they had a blue-tick verification on ≥2 social media (SM) and an active WM blog. A sample of blog posts were systematically evaluated against thirteen credibility indicators under four themes: ‘transparency’, ‘use of other resources’, ‘trustworthiness and adherence to nutritional criteria’ and ‘bias’. Indicators were yes/no questions to determine an overall credibility percentage for each SMI. The ten most recent meal recipes from each blog were evaluated against Public Health England’s (PHE) calorie targets and the UK ‘traffic light’ food labelling scheme to assess nutritional quality. Percentages ranged from 23–85%, the highest gained by a Registered Nutritionist. SMI blogs may not be credible as WM resources. Given the popularity and impact of SM in the context of overweight, obesity and WM, this study may inform the methodological approach for future research.