The combined group will produce 1 million ounces of gold a year, CEO Sébastien de Montessus said, making it larger than Newmont Goldcorp and Barrick in West Africa. Endeavour is already the top gold producer in Cote d'Ivoire.
Endeavour shareholders will own about 70% of the combined company, with Semafo shareholders holding the rest.
There is potential for expansion at the Mana project, de Montessus said, also highlighting the Bantou exploration project which lies just south of Endeavour's existing Houndé mine.
He added, however, that further optimisation of the company's mine portfolio was possible.
Under the deal, Semafo shares will be exchanged at a ratio of 0.1422 Endeavour shares for each Semafo share, which represents a premium of 54.7% from the closing price of Endeavour and Semafo on Friday, an Endeavour statement said.
The deal was set to close in June, and de Montessus said the coronavirus pandemic was unlikely to disrupt the planned takeover. Endeavour last week reported an employee at its Houndé mine tested positive for the coronavirus.
Mining shares have plummeted due to the coronavirus pandemic slowing the world economy and bruising financial markets, making dealmaking more attractive.
Global miner BHP said earlier this month it is in good shape to act if disruption from the virus brings M&A openings.
Semafo shares have halved in value since the start of November last year, when a convoy of employees was attacked near its Boungou mine in eastern Burkina Faso, causing 39 deaths and halting operations at its Boungou mine.
But de Montessus said the deal's timing was not linked to the virus and discussions with Semafo have been ongoing for 14 months.
"After the attack, I think Semafo probably felt that two mines in a consolidating market was not enough, and that teaming up with Endeavour was a good way to grow," said de Montessus.
Semafo said last month it expects to restart mining at Boungou in the fourth quarter. De Montessus said he is "confident" the mine can restart before then.
"Despite the dramatic security issue back in November, Boungou is a great asset on which Semafo has done limited exploration so far," he said.
Endeavour has been looking at the new security plan for Boungou, de Montessus added, without giving details. He said he informed Burkina Faso's president about the transaction, and that he was "very happy" and "supportive".
"I believe the combination of the two groups will help reinforce the overall security around our different mine sites," said de Montessus.
(Reporting by Helen Reid and Arathy Nair, editing by Louise Heavens and Nick Zieminski)
By Helen Reid