Weatherford, whose shares rose 10 percent in extended trading, said in a statement McCollum was expected to join the company in late April.
McCollum will be replaced at Halliburton, the world's No. 2 oilfield services provider, as interim CFO by Executive Vice President Robb Voyles.
Weatherford said interim CEO Krishna Shivram would leave the Houston-based company with immediate effect. He took the job in November, when former CEO Bernard Duroc-Danner left the company.