The Speaker, Seoule Simeon, ruled that Gracia Shadrack, the MP for Malekula, should lose his seat for missing three consecutive sittings.
Mr Shadrack was alleged to have not advised the clerk of Parliament about his absences.
But he claimed he had submitted his medical certificate on time to show that he could not attend Parliament because he was sick.
The Opposition MP challenged the Speaker's decision in the Supreme Court.
Vanuatu's Chief Justice Vincent Lunabek has made a ruling, allowing Mr Shadrack to resume his duties in Parliament.