Abdul Razak Baginda, a close associate of the new prime minister who was sworn in last week, had been accused of ordering police to kill his former lover after she came to his family home to harass him for money.
But last year he was acquitted of abetting the 2006 slaying of the 28-year-old model and interpreter -- a case which, with its ingredients of sex, politics and violence, has fascinated the nation.
Altantuya's body was blown up with military-grade explosives in a jungle clearing, leaving only shattered bone fragments as evidence.
The two officers found guilty of the murder, Chief Inspector Azilah Hadri and Corporal Sirul Azhar Umar, are from an elite unit that guards top ministers.
"Each of them are blaming the other, they failed to raise reasonable doubt against the prosecution's case. I convict both of you as charged," said Shah Alam High Court judge Zaki Mohamad Yasin.
"I sentence both of you to death. You will be taken to a place of execution where you will be hanged by your neck until you are dead," he said.
The pair looked calm when the sentence was handed down, and then stepped out of the dock and hugged their lawyers, who later said they would file an appeal.
Sirul has said he was a "scapegoat" and Azilah's fiance, Nur Azila Baharuddin, insisted the pair were not guilty.
"We expected him to be acquitted but the judge has made the decision. We will wait for the next stage," she told reporters. "I really want to marry him, I have been waiting for so long since 2006."
Malaysia's top blogger Raja Petra Kamaruddin has been charged with sedition after repeatedly linked Najib and his wife to the murder on his popular website Malaysia Today.
Najib has vehemently denied any involvement in the killing and said he never even met Altantuya, but despite any evidence linking him to the case, the allegations persist and the opposition has called for an official inquiry.
Leading opposition figure Lim Kit Siang said Thursday that the mystery surrounding the case was "haunting and hounding" Najib and threatened to damage his administration and the nation's reputation.
"(The) conviction and death sentence have not lessened but intensified public demands and necessity for a Royal Commission of Inquiry into swirling allegations of Najib's involvement," he said in a statement.
Karpal Singh, an opposition politician and leading lawyer who is representing Altantuya's family, also said the verdict would fail to quell speculation over the case.
"You must satisfy the international community. The international community does not accept that only these two are responsible for the murder. It goes beyond these two," he told reporters.
"These two have no motive, they didn't even know her before."
Altantuya's father Setev Shaariibuu was distraught over the acquittal of Abdul Razak Baginda last year, in a case seen as a test of the strength of Malaysia's much-criticised judiciary.
"I am not satisfied. My daughter knows only one Malaysian and it is Razak Baginda. Now my daughter is dead and Baginda is freed... the country has lost credibility in the world," he told reporters at the time.
Setev Shaariibuu was not present in court on Thursday.
Agence France-Presse - 4/9/2009 8:30 AM GMT