Trans and gender diverse adults are at increased suicide risk. Optimism protects against suicide across multiple populations. Applying the Interpersonal-Psychological Theory of Suicide (IPTS), we examined both factors among 237 adults recruited via social media and online platforms, 79.3% of whom reported serious suicide ideation. Dispositional optimism predicted suicidal ideation and behaviors (SIB), but did not moderate the relationship between the IPTS components and SIB. After controlling for depressive symptoms, hormone therapy and gender-affirming surgery did not predict SIB. Promoting dispositional optimism within a therapeutic framework may reduce SIB in this vulnerable population.