Abstract: Techniques are provided to enable non-disruptive upgrades of multipath device drivers. A multipath device driver includes a core module and a thin module. The core module is configured to implement all multipathing functionality of the multipath device driver, and the thin module is configured to create and maintain an instance of a multipath device, which is utilized by the core module to control I/O operations over a plurality of I/O paths from the host system to an array of data storage devices. In response to an upgrade command, the thin module replaces I/O entry points of the core module so that I/O operation requests are routed to the thin module during an upgrade operation of the core module. The thin module utilizes the instance of the multipath device during the upgrade operation to execute the I/O operation requests that are routed to the thin module.