This chapter advances three forms of justice (procedural, social, epistemic) as tools for ethical patient involvement in HTA. They provide important insights for questions facing practitioners seeking to involve patients in HTA: why should we involve patients (justification), which patients should we involve (representation) and how should we involve patients (operationalisation). A procedural justice approach sets important standards to ensure patient involvement efforts in HTA adhere to fair processes. However, a narrow procedural lens can lead to entrenched and rigid processes that no longer align with procedural justice; social justice and epistemic injustice provide additional considerations to advance ethical patient involvement in HTA. Employing a social justice lens would help patient involvement processes attend to problems of systemic marginalisation and facilitate the participation of those who are underrepresented in participatory processes. Finally, epistemic injustice considerations would ask practitioners to think about how patient input is considered alongside clinical, economic and other forms of input that have historically garnered authority in HTA. Epistemic injustice may arise if patient input is undervalued or excluded due to exclusionary practices or biases. Together, the forms of justice strengthen the rationales for patient involvement in HTA and link rationales with consequential representation and operationalisation decisions.