Systems and methods are disclosed for electronic transaction messaging conversion. One method comprises receiving an authorization request message from a point of sale (POS) device, the authorization request message comprising transaction data associated with a transaction. Upon validating the authorization request message, a provisional authorization response message may be generated and sent to the POS device. Subsequently, a capture message may be received from the POS device, requesting clearing and settlement of the transaction. The capture message may be validated and translated to a composite message that is single-message system (SMS)-compatible. The composite message may then be sent downstream for further processing.