Uber completed the $3.1 billion acquisition of Careem's businesses across the Middle East.
The Dubai ride-hailing company retains operational and brand independence even as it becomes a wholly-owned subsidiary of the American firm. Careem co-founder Mudassir Sheikha also remains chief executive.
Its board will be made up of three representatives from Uber and two representatives from Careem.
The closing of the deal, initially announced in March, means that Uber now owns Careem's mobility, delivery, and payments businesses across the region, including in Egypt, Jordan, Saudi Arabia, and the UAE.
On Monday, the acquisition was given the go-ahead by the Egyptian Competition Authority, clearing a key regulatory hurdle.
However, regulatory approval is still pending in Pakistan, Qatar and Morocco, which means the deal has not yet closed in those countries, the companies said on Friday.
In an email sent to the staff of both firms, Uber chief executive Dara Khosrowshahi said that "working in parallel, our two brands will be able to build upon the unique strengths of each, to the benefit of drivers… riders, and the cities we serve across the greater Middle East".
Mr Sheikha wrote in a response that “we have a great deal of respect for Uber from our days of competing with you, and we look forward to working alongside you all to accelerate the size and speed of our collective impact”.
San Francisco-headquartered Uber's purchase of Careem marked the region's biggest technology sector acquisition to date.