A man sacked for posting an expletive-laden rant against his senior work colleagues on Facebook has lost an unfair dismissal claim.

Damien O'Keefe, who was employed for four years at a Good Guys store in Townsville, took to the social networking site at home on his day off to express frustration at long-running pay problems.

"Damien O'Keefe wonders how the f--- work can be so f---ing useless and mess up my pay again," the May 2010 status update said.

"C---s are going down tomorrow."

Fair Work Australia heard that the employer, trading as Troy Williams The Good Guys, sacked Mr O'Keefe after interpreting the final comment as "a threat" to operations manager Kelly Taylor.