Astrocytes regulate multiple aspects of neuronal and synaptic function from development through to adulthood. Instead of addressing each function independently, this review provides a comprehensive overview of the different ways astrocytes modulate neuronal synaptic function throughout life, with a particular focus on recent findings in each area. It includes the emerging functions of astrocytes, such as a role in synapse formation, as well as more established roles, including the uptake and recycling of neurotransmitters. This broad approach covers the many ways astrocytes and neurons constantly interact to maintain the correct functioning of the brain. It is important to consider all of these diverse functions of astrocytes when investigating how astrocyte-neuron interactions regulate synaptic behavior to appreciate the complexity of these ongoing interactions.