T-Mobile's long-time Chief Executive John Legere is stepping down from his position effective immediately as part of the deal.
Legere was originally set to leave at the end of April, with Mike Sievert, T-Mobile's president, as his successor. Legere will serve on T-Mobile's board of directors.
The combined company will now operate under the T-Mobile name and will trade on the NASDAQ as "TMUS."
Sprint acknowledged risks in an SEC filing, saying that its internal controls over financial reporting could negatively impact the combined company.
A US federal judge approved the deal in February, rejecting a claim by a group of states that the proposed transaction would violate antitrust laws and raise prices.
As part of an agreement with the Department of Justice, the combined wireless company will sell off assets to Dish Network, making the latter the fourth-largest provider in the US wireless space.