Aras Mohammed Hamid, 27, and Shivan Hayder Azeez Zangana, 21, known as Azeez, were jailed for seven years and three years respectively.
They were convicted in December of preparing acts of terrorism.
A third man, Ahmed Ismail, 19, was jailed for 18 months for failing to alert authorities to their plot.
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Azeez, of Washington Road, Sheffield, was sent to the UK by his family to keep him safe after battling extremists with the Kurdish Peshmerga separatist group, Kingston Crown Court heard.
He was turned by fellow Kurd, asylum-seeker Hamid, and agreed to change sides and go with him to fight for IS.
The two were discovered by police sleeping at a Birmingham mosque on 17 May, days after several of Azeez's worried relatives had called 999 with concerns about what he was planning.
He had fled his home and bought a plane ticket from Gatwick to Sulaymaniyah in northern Iraq.
While Azeez was arrested at the mosque in Holyhead Road, Handsworth, Hamid, of no fixed address, had items confiscated but was not detained.
He was discovered two days later hiding in a lorry on the A2 near Dover, Kent, while trying to smuggle himself out the UK. He had a fake Bulgarian passport.
Hamid was also convicted of assisting another in commission of terrorist acts and admitted a charge of possession of an identification document with improper intent.
Ismail, of Portwrinkle Avenue, Coventry, was convicted of failing to disclose information about acts of terrorism.
Hamid and Azeez were each ordered to serve an extended period of 12 months on licence at the end of their sentences.
Two Kurds living in the UK are jailed for terror offences after trying to join so-called Islamic State fighters in Iraq.