It is alleged widespread human rights abuses took place in Marange
Zimbabwe has escaped suspension from the Kimberly process - the certification scheme which regulates the sale of so-called blood diamonds.
Instead, the 70-member international diamond trade body has agreed to give Zimbabwe more time to reform its mining practices.
Rights groups alleged soldiers killed about 200 people at a diamond field last year, which the government denies.
The decision came as talks to save the unity government started in Mozambique.
The coalition administration - formed in February - has been in crisis since Prime Minister Morgan Tsvangirai began boycotting cabinet meetings last month.
Mr Tsvangirai is protesting at the way President Robert Mugabe is implementing the power-sharing deal.
The BBC's southern Africa correspondent Karen Allen says the compromise diamond deal agreed in Namibia is likely to anger human rights groups.
President Mugabe says he has met his side of the unity deal
Although its own investigators found killings and forced evictions from the Marange diamond fields in the east of the country close to the border with Mozambique, the Kimberley Process panel stopped short of kicking Zimbabwe out, she says.
Instead it has adopted a plan - proposed by Zimbabwe itself - which includes calls for an independent inspector to monitor diamonds leaving the controversial fields.
Human rights groups claim the diamonds have been an important source of revenue for the military and for President Mugabe's Zanu-PF party.
Meanwhile, Mr Mugabe and Mr Tsvangirai are both attending the talks in Mozambique organised by leaders of the Southern African Development Community (Sadc).
Former opposition leader Mr Tsvangirai has accused his long-time rival of being a "dishonest and unreliable partner" in the power-sharing deal, which was struck last year.
The opposition MDC party also accuses Mr Mugabe's Zanu-PF party of persecuting its officials.
Zanu-PF has described the accusations as "propaganda".
Human Rights Watch recently urged Sadc leaders to press Zanu-PF to end what it called "ongoing human rights abuses".