The versatile defender will link up with the League Two club until January 10th 2015.
O’Connor, 21, spent the majority of last season on loan at fellow Devon club Torquay United, making 32 appearances. The previous campaign was also spent out on loan where he was an ever-present for Burton Albion.
A Republic of Ireland Under-21 international, O’Connor has been with Rovers since the age of 16.
Argyle get their season under way this Saturday with an away match against newly promoted Cambridge United.