After the Australian Senate did not pass the law allowing marriage equality, a same bill was rejected in Tasmania.
The Legislative Council (the state upper house) thus decided not to allow marriage for all.
According to The Sydney Morning Herald, Australian Marriage Equality spokesman Rodney Croome said lower houser approval and some backing in the council were great achievements, given that Tasmania was last to decriminalise homosexuality (1997).
"If opponents of this bill think they have put the debate to bed they are wrong," Mr Croome said.
The defeat is the result of some MPs constitutional doubts.