In this study, we tested the validity across two scales addressing conspiratorial beliefs that may influence behaviors related to public health, government, and the COVID-19 pandemic. The 4-item Conspiratorial Thinking Scale and 3-item Anti-Expert Sentiment Scale were validated across 24 languages and dialects using the COVIDiSTRESSII Global Survey dataset, with 12,261 participants who completed the survey in languages with greater than 100 participants per language. We employed confirmatory factor analysis, measurement invariance test, and measurement alignment for internal consistency testing. To test convergent validity of the two scales, we assessed correlations with trust in seven agents related to government, science, and public health. Although scalar invariance was not achieved when measurement invariance test was conducted initially, we found that both scales can be employed in further international studies with measurement alignment. Moreover, both conspiratorial and anti-expert beliefs were significantly and negatively correlated with trust in all agents. Findings from this study provide supporting evidence for the validity of both scales across 24 languages for future large-scale international research.