Disclosed are various examples for single-sign on by way of managed mobile devices. For example, an identity provider service can receive a request for an identity assertion from an application executed in a client device. The identity provider service can then detect a platform associated with the client device. A response to the request can be sent based at least in part on the platform, where the response requests authentication by a management credential. Data generated by the management credential is received from the client device, and the management credential is determined to be valid for the identity assertion. The identity assertion is then sent to the client device in response to determining that the management credential is valid for the identity assertion.