A smartphones with Sprint logo are seen in front of a screen projection of T-mobile logo, in this picture illustration taken April 30, 2018. REUTERS/Dado Ruvic/Illustration
The decision is expected to be made public on Tuesday.
The third-largest U.S. wireless carrier by subscribers has been awaiting a decision from a federal judge on whether it can move forward with its $26.5 billion merger with Sprint.
The two companies are expected to start talks on renegotiating the terms of their merger in the next few days, the sources said.
Multiple states had sued to block the deal, arguing it is anticompetitive and will raise prices for customers.
Sprint did not immediately respond to a Reuters request for comment, while T-Mobile declined to comment.
Shares of Sprint were up 50% at $7.2 in after-market trading, while T-Mobile rose 6.5%.
The Wall Street Journal earlier reported that the court was expected to approve the deal on Tuesday.
Reporting by Arundhati Sarkar in Bengaluru; Editing by Shailesh Kuber and Uttaresh.V