Zimbabwe's Constitutional Court confirmed President Emmerson Mnangagwa's disputed July 30 election victory on Friday, dismissing an opposition challenge that had held up his inauguration, which will now be held on Sunday.
Mnangagwa's also reiterated his call for peace and unity in the country.
Chamisa had argued in his application that Mnangagwa colluded with Zec to rig the election through ballot staffing, vote buying and manipulation of the result.
In a unanimous ruling of the nine judges of the country's top court, Chief Justice Luke Malaba said Chamisa had failed to prove allegations of fraud during the presidential vote.
A spokesman for Zimbabwe's ruling party says the inauguration of President Emmerson Mnangagwa will be on Sunday after the constitutional court upheld his election win.
Zimbabwe's justice minister, Ziyambi Ziyambi, refused to grant permission to South African lawyers Jeremy Gauntlett, Dali Mpofu and Tembeka Ngcukaitobi to represent MDC Alliance leader Chamisa in Wednesday's constitutional court hearing, with the lawyers claiming this could have affected the case.
Another opposition leader said that he still believes elections were unfair. "Let us all now put our differences behind us", he said.
The election, in which Mnangagwa and Chamisa were the main contenders, was touted as a crucial step toward shedding Zimbabwe's pariah reputation and securing worldwide donor funding to revive an economy suffering chronic shortages of investment and cash, as well as high unemployment.
This was the first election after the end of Robert Mugabe's 37-year rule, which was marked by rigged elections. "It is time to move forward together".
In those anxious days, six people were killed in clashes between security forces and protesters, and police raided the opposition party's offices.
Mangagwa needs global legitimacy to obtain the multibillion-dollar bailouts required to avoid economic breakdown.
Worldwide monitors largely praised the conduct of the election itself, although European Union observers said that Mnangagwa, a former long-time Mugabe ally, benefited from an "un-level playing field". It also alleged that some polling stations recorded more voters than those registered.
Campaigning was more open than previous votes, but the election was marred by violence and a crackdown on opposition activists.