Steroid hormones like estrogens have been traditionally considered to be circulating factors secreted by peripheral glands to impact brain function and behavior over long-term timescales (days-weeks). We now understand that estrogens in particular can be synthesized by neurons at synaptic junctions to have acute (secs-mins) actions on neural circuit function and behavior. Our work in this domain focuses on an auditory pathway in the songbird forebrain that exemplifies this capacity for local ‘neuroestrogen’ synthesis and action. We have developed evidence that brain-derived estrogens can fluctuate dynamically and locally when adults and juveniles hear songs, and that steroids can have minute-by-minute actions on auditory neuronal coding and communication behaviors. More recently, we have characterized the actions of estrogens on membrane receptors that regulate intrinsic and network properties of auditory neurons, as well as the way that estrogen synthesis guides learning of new sounds in juveniles and adults. Evidence from in vivo electrophysiology, patch clamp electrophysiology, in vivo microdialysis, and behavioral experiments will be discussed. Together, several lines of research from my lab and others is showing that brain-derived estrogens can act as neuromodulators of neural circuit function and sensorimotor-dependent behaviors.