Cairney joins the League One side after leaving Kilmarnock while Keenan, 21, made six appearances for Partick Thistle last season.
"They are two great additions to the club," manager Brian Reid told Stranraer's official website.
"Getting someone like Paul with his wealth of experience is quite a coup."
Former Partick Thistle and Hibernian player Cairney, 27, played 16 times for Killie last season despite some injury problems.
Stranraer missed out on promotion to the Championship at the end of the 2014-15 campaign after losing to Forfar in the play-offs.
Stranraer have added top flight experience to their squad by signing midfielder Paul Cairney and defender Dale Keenan.