Gabriel Rasmus, 30, of Birmingham, who had previously admitted preparing for terrorist acts, was sentenced to four years and three months.
Somalia-born Anas Abdalla, 27, who was found guilty of the same offence on 13 October, was sentenced to five years.
They were brought to justice after being befriended by an undercover police officer named "Muhamed".
A third man, Mahamuud Diini, 27, was cleared after a trial earlier this year.
The court heard all three men were arrested when they were found hiding in a truck at the Kent port on April 3 last year.
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Prosecutor Karen Robinson told the Old Bailey that Rasmus and Abdalla had planned to "join forces with Islamic State to offer their services, together with their lives if need be".
Ms Robinson told the court Rasmus, who comes from a Christian family and converted to Islam in 2008, said if he had to "stay in this country he would commit some terrorist attack here".
According to Ms Robinson, he also said: "I don't want to do something here until I keep trying to go there first."
Rasmus, of Chain Walk, Lozells, moved to the UK from South Africa in 1999 and has four children with three different women.
Judge Richard Marks QC said he did not accept his claims that he planned trips to Istanbul for a holiday and for work.
Ms Robinson also told the court Somalia-born Abdalla, of Fox Hollies Road, Acocks Green, was heard complaining about his work and "having to work with non-Muslims".
Jurors were told how former asylum seeker said: "September 11 was so good."
The men were brought to justice after "Muhamed" secretly recorded their conversations.
Assistant Chief Constable Marcus Beale, from West Midlands Police, said: "Today's sentences send a clear message to hopefully deter anyone planning to travel to Syria to join Daesh."
Diini, of Coventry Road, Small Heath, Birmingham, was cleared after a trial earlier this year.
Two men stopped at Dover trying to travel to Syria to join so-called Islamic State have been jailed.