The constitutional court in N'Djamena said on Sunday their applications had been rejected over "irregularities."
They vowed at a press conference to "fight" back and block the road they say the ruling Deby dynasty is following to "dictatorship."
Denouncing the court's "fallacious reasons," one of the 10 read out a statement they had all signed calling for the mobilization of the nation's people, using all legal means "to save the country from dictatorship."
The appeal comes a month after Chadian leader General Mahamat Idriss Deby Itno's main rival Yaya Dillo was shot dead in an army assault on his PSF party headquarters.
Dillo's replacement, Nassour Ibrahim Koursami, was among those barred, along with prominent opponent Rakhis Ahmat Saleh.
"Yesterday, Yaya Dillo was executed without warning and today (the authorities) are doing everything to disqualify inconvenient candidates and to pave the way for the dynasty," the protesting candidates said.
General Deby was among 10 candidates the council allowed to stand.
He was proclaimed president by a junta of generals in 2021 following the death of his father, who had ruled the Sahel country with an iron fist for more than three decades.
Political analysts, diplomats and opposition figures agree that the other approved candidates have been nominated to give a pluralist veneer to the ballot or had no political support and little chance of winning.
Human Rights Watch (HRW) has called for an independent investigation into the murder of Yaya Dillo, arguing that the army assault "raises serious concerns about the environment for elections scheduled for May."
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