President Abdulla Yameen narrowly escaped injury when a blast struck the boat he was using to return home from the airport last September.
His then-deputy Ahmed Adeeb was arrested weeks later and charged with high treason.
He was sentenced to 15 years in prison on Thursday, days after receiving a 10-year sentence for owning firearms.
Adeeb denied playing any part in the blast, which the prosecution maintained was caused by a bomb, although the US Federal Bureau of Investigation said no bomb exploded.
In recent years, the Maldives has been rocked by political infighting.
“The criminal court has barred me from calling the trial unfair, but we have concerns and intend to launch an appeal immediately,” Adeeb’s lawyer, Moosa Siraj, told the Maldives Independent website.
“This was by no means a fair trial,” Adeeb’s second wife, Mariyam Nashwa, told the Maldives Independent.
“The investigation was nowhere near complete. I think they closed the trial because they are afraid Adeeb might say something.”
Two of Adeeb’s bodyguards were given 10-year sentences for their role.
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Image courtesy of AFP