A speech-processing system may provide access to multiple virtual assistants via one or more voice-controlled devices. Each assistant may leverage language processing and language generation features of the speech-processing system, while handling different commands and/or providing access to different back applications. Different assistants may be available for use with a particular voice-controlled device based on time, location, the particular user, etc. The voice-controlled device may include components for facilitating user interaction with multiple assistants. For example, a multi-assistant component may facilitate enabling/disabling assistants, assigning gestures and/or wakewords, etc. The multi-assistant component may handle routing commands to a command processing subsystem corresponding to an assistant invoked by the command. The voice controlled device may further include observer components, each configured to monitor the voice-controlled device for invocations of a particular assistant.