Arriving at the village of Dob pri Mirni in the south-east accompanied by his wife, close aides and supporters, Janša was greeted by a crowd of some 3,000, who rallied for his freedom and the rule of law not far from the prison.
In an hour-long emotional farewell, a number of SDS officials and supporters addressed the rally at the gates of the country's biggest prison, pledging to do everything in their power to overturn what they consider a shameful and unjust conviction which was made to disqualify a political opponent.
In addressing the rally, the former prime minister draw a parallel with the infamous 1988 JBTZ trial in which was sentenced to 18 months in prison by a Yugoslav military court in Ljubljana for stealing classified documents while working as a journalist.
He said the trial from 25 years ago gave the final impetus to Slovenia's independence efforts, but while Slovenia became independent in 1991 it had never became free of lies and deceit, adding that Slovenia was yet to become a rule of law.
Janša, whom many see a Slovenian independence-era hero, closed his address by urging the people to "colour the country in the colours of freedom and justice" at the 13 July general election, in which he will run for a seat in parliament from prison.
Janša walked down the street towards the prison accompanied by a river of people carrying Slovenian flags and banners demanding his freedom and justice, singing the Slovenian anthem in front of the prison.
The SDS leader was found guilty of accepting the offer of a bribe in his capacity of prime minister as the Slovenian government and Patria were negotiating a deal on the purchase of armoured personnel carriers for EUR 278m. A relevant contract was signed in 2006.
The case is however not completed yet, as Janša is now challenging the verdict at the Supreme Court (which usually takes several months) after the Constitutional Court rejected his appeal earlier this week on a technicality (he did not yet use all legal means at his disposal).
Ever since the start of the Patria scandal in Slovenia, which broke out with a Finnish documentary before the 2008 elections, Janša has maintained his innocence and his SDS has stood firmly behind its leader, blaming the guilty verdict on a show trial organised by his political opponents.
Janša was convicted alongside co-defendants Tone Krkovič, a retired army officer, and Ivan Črnkovič, the boss of Patria's local partner in Slovenia, for being part of a scheme to distribute profit from the EUR 278m public contract with Patria.
The Ljubljana Local Court sentenced him to two years in prison and a EUR 37,000 fine on 5 June 2013, which was upheld in full in late April by the Higher Court in Ljubljana. Krkovič and Črnkovič each got 22 months in prison and fines of EUR 37,000.
Janša has previously vowed to fight the conviction all the way to the European Court of Human Rights.