The two will create a new global pharmaceutical company.
Upjohn, makes medications Lipitor, Celebrex and Viagra. Mylan is best known for its EpiPen, an injector used to halt life-threatening allergic reactions.
Pfizer shareholders will own a majority of the combined company, according to a press release on Mylan’s website.
The boards of directors for both companies have unanimously approved the agreement.
The deal Monday arrives at a precarious time for big drug makers who are threatened by patent protection losses and lower-priced rivals.
The new company will be incorporated in Delaware and run operations in Pittsburgh, Shanghai and Hyderabad, India.
The combination is expected to close in the middle of next year.
We're continuing to follow this developing story. Refresh WPXI.com for updates.
The Associated Press contributed to this report.
Cox Media Group