Austria's highest tribunal however knocked six months off a sentence passed by a lower court in March of three and a half years in prison for the disgraced centre-right politician.
He will have to go to jail in the coming weeks.
Strasser, interior minister from 2000-4, was secretly filmed in 2010 by undercover reporters from Britain's Sunday Times newspaper saying that he charged €100,000 ($126,800) a year to influence the drawing up of EU laws.
"Of course I am a lobbyist," a video of one of the reporters' meetings with Strasser showed him saying.
"But the fee, my clients pay me for a year €100,000, yes. I now have five, hopefully from tomorrow six clients… You will be the seventh."
Strasser, now 58, resigned in 2011 after the Sunday Times broke the story.
The sting aimed at exposing corruption in Brussels also ensnared three other MEPs: Romania's Adrian Severin, Slovenia's Zoran Thaler and Pablo Zalba from Spain. Zalba was cleared by the European Commission Anti-Fraud Office (OLAF) of any wrong-doing.
Strasser was initially sentenced to four years in prison in January 2013 but the verdict was overturned in November because of a procedural error, necessitating a further trial which saw him sentenced again this March.
He has always claimed his innocence, saying that he believed the reporters, who posed as lobbyists wanting to change EU directives on waste management and financial services, were spies.
He remained a free man Monday but will have to begin his jail term within four weeks of being notified formally of his sentence. After six months behind bars he will be able to apply to be released and wear an electronic tag.