Biotic and abiotic stresses constrain plant growth worldwide. Therefore, understanding the molecular mechanisms contributing to plant resilience is key to achieving food security. In recent years, proteins containing dopamine β-monooxygenase N-terminal (DOMON) and/or cytochrome b561 domains have been identified as important regulators of plant responses to multiple stress factors. Recent findings show that these proteins control the redox states of different cellular compartments to modulate plant development, stress responses, and iron homeostasis. In this review, we analyze the distribution and structure of proteins with DOMON and/or cytochrome b561 domains in model plants. We also discuss their biological roles and the molecular mechanisms by which this poorly characterized group of proteins exert their functions.