Volos were kicked out of the Europa League by UEFA and handed a three-season ban for a probationary five-year period from continental competition last August for their involvement in a match-fixing scandal.
The club took their case to CAS but it has been rejected.
"The Court of Arbitration for Sport has rejected an appeal lodged by Greek club Olympiakos Volos against the decision by the UEFA Appeals Body last August to confirm the club's exclusion from the 2011/12 UEFA Europa League," UEFA said on their website.
Greece's biggest match-fixing scandal erupted in June and led to more than 80 people being charged while Volos President Achilleas Beos was banned for life from all football activities.
Greek football has been plagued by match-fixing problems in recent years and a recent survey conducted by the International Federation of Professional Football Players (FIFPro) highlighted the country as one of Eastern Europe's worst-affected.
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