Background: Transgender and gender diverse young people (TGDY) are at higher risk of psychosocial distress relative to their cisgender counterparts. TGDY rely heavily on their parents to support their desired affirmation and to facilitate access to legal and medical affirmation. While it is well understood that parent conflict negatively impacts the well-being of children and young people, little is known about how parental conflict and parental affirmation support are related to TGDY well-being. Aims: The aim of the present study was to (1) explore affirmation experiences of TGDY, as reported by their parents, focusing in particular on parental support for affirmation and barriers to affirmation, and (2) test whether parental support and aspects of the coparenting relationship predicted TGDY mental health outcomes. Method: A sample of 63 parents (Mage = 45.71 years) of TGDY (aged 11 to 17 years) completed an online survey. Results: Almost 90% of the TGDY reported on had socially affirmed their gender, though fewer had taken steps to legally or medically affirm their gender. Parental support for affirmation was generally very high, and reported discrepancies between coparents were generally low; however, discrepancies were greatest for medical affirmation. Finally, parent support for affirmation was a strong predictor of lower TGDY depressive symptoms, though parental conflict did not predict TGDY mental health. Conclusion: Results highlight the important role of parental support for gender affirmation. Further research is needed to track the role of parental support and affirmation on TGDY well-being over time, and to ensure that such research is completed with more diverse samples.