The largest deals are not the most successful ones. Exxon and Mobil worked. Kraft Heinz destroyed value. AT&T bought Time Warner for $85 billion and spun it off four years later. Google paid roughly $50 million for Android, which is the best return on this list by a wide margin.
Thirteen of the biggest transactions, what each cost, and what happened next. Last updated September 2026.
| Deal | Year | Approx. value | Outcome |
|---|---|---|---|
| Verizon and Vodafone | 2014 | $130bn | Full control of Verizon Wireless |
| Bristol-Myers Squibb and Celgene | 2019 | $74bn | Leading oncology portfolio |
| Kraft and Heinz | 2015 | $100bn combined | Substantial value written down |
| Pfizer and Warner-Lambert | 2000 | $90bn | Control of Lipitor |
| AT&T and Time Warner | 2018 | $85bn | Divested in 2022 |
| Exxon and Mobil | 1998 | $80bn | Still cited as a model merger |
| Raytheon and United Technologies | 2020 | Merger of equals | Created an aerospace and defence major |
| Salesforce and Slack | 2021 | $27.7bn | Integrated into Customer 360 |
| Facebook and WhatsApp | 2014 | ~$19bn | Reach into markets Facebook lacked |
| Microsoft and Nuance | 2021 | $19.7bn | Healthcare AI capability |
| Disney and Pixar | 2006 | $7.4bn | Franchises worth many times the price |
| Disney and Marvel | 2009 | $4bn | One of the best-returning deals ever |
| eBay and PayPal | 2002 | $1.5bn | Spun off in 2015, worth far more |
Tens of thousands of mergers and acquisitions complete every year, from multinational transactions to small regional deals. Bloomberg Law counted 48,833 in 2023, a year widely regarded as slow.
The ones below are among the largest ever recorded. Read them for what happened afterwards rather than for the headline figure.
Verizon and Vodafone jointly owned Verizon Wireless. In 2014 Verizon bought out Vodafone's 45% stake for around $130 billion, taking full ownership.
Dubbed the deal of the decade at the time. Verizon's performance in the years that followed justified the description.
Announced in January 2019 and completed that November, at approximately $74 billion. One of the largest pharmaceutical transactions ever.
BMS absorbed Celgene's oncology portfolio, including Revlimid and Abraxane, creating a biopharmaceutical company weighted heavily toward cancer treatment. The combined business operates as Bristol Myers Squibb.
H.J. Heinz and Kraft Foods merged in 2015 to form The Kraft Heinz Company, a combination valued at roughly $100 billion and expected to enter the world's ten largest food businesses.
It has not gone as planned. The company subsequently wrote down billions in the value of its own brands, and analysis generally attributes the difficulty to consumer preferences shifting away from packaged processed food faster than the business adapted.
A useful counterweight to the assumption that scale delivers value on its own.
Pfizer acquired Warner-Lambert in 2000 for around $90 billion, in one of the most hostile acquisitions on record.
Warner-Lambert had agreed to be acquired by American Home Products. Pfizer intervened with a higher offer, American Home Products withdrew with substantial break fees, and Pfizer prevailed.
The prize was Lipitor, which became one of the best-selling drugs in pharmaceutical history.
AT&T first bid for Time Warner in 2016. The US Department of Justice sued to block it on competition grounds, AT&T won in court, and the $85 billion deal completed in 2018.
Four years later AT&T spun the business off, combining it with Discovery to form Warner Bros. Discovery. A deal that survived a government challenge and was then unwound, which makes it a better lesson than most of the successes on this list.
In 1998 the first and second-largest US oil producers combined in a deal worth around $80 billion.
It attracted scepticism at the time on both competition and integration grounds. It is now generally cited as one of the more successful large mergers, having produced a business that held its position for decades.
Announced in 2019 and completed in April 2020, creating Raytheon Technologies.
Structured as a merger of equals rather than an acquisition, with both companies contributing their aerospace businesses. The combined entity had pro forma revenue around $74 billion and roughly 195,000 employees.
Salesforce acquired Slack in 2021 for $27.7 billion, at the time the second-largest software acquisition ever.
The rationale was integrating real-time communication into the Customer 360 platform, and using Salesforce's enterprise reach to extend Slack's user base.
Announced in 2014 at approximately $19 billion, with the final value closer to $22 billion by completion as Facebook's share price rose.
The strategic logic was reach into developing markets where Facebook was not dominant and WhatsApp already was. It also brought mobile messaging capability into an ecosystem that lacked it.
Microsoft acquired Nuance in 2021 for $19.7 billion, buying speech recognition, natural language processing and clinical imaging technology.
The focus was healthcare and customer service AI, with Nuance's products moving onto Azure.
Disney acquired Pixar in 2006 for $7.4 billion, a figure widely considered high at the time.
What followed included WALL-E, Toy Story 3 and a run of films generating many billions. The acquisition also brought Pixar's leadership into Disney animation, which is often credited with reviving it.
Three years later Disney bought Marvel Entertainment for around $4 billion.
Iron Man had been released the previous year and performed strongly, but nobody forecast what followed. The Marvel Cinematic Universe went on to become the highest-grossing film franchise ever, making this one of the best-returning acquisitions in corporate history.
eBay acquired PayPal in 2002 for approximately $1.5 billion, when more than 70% of eBay auctions already used it as the preferred payment method.
PayPal ran as a subsidiary with its own culture rather than being absorbed, and eBay spun it off as an independent public company in 2015. By then PayPal was worth many multiples of the purchase price.
A reminder that not integrating is sometimes the right answer.
Looking across the thirteen, the deals that worked tend to share three things.
A specific asset, not general scale. Lipitor, Android, Marvel's characters. Kraft Heinz was built on scale alone.
Integration matched to the asset. Disney integrated Pixar's talent deeply. eBay deliberately did not integrate PayPal. Both were right for what they bought.
Retention of the people who made it valuable. An acquisition made for expertise that loses that expertise has bought a logo.
That last point is where most value is lost. Cross-border deals add a further complication: if the target has staff in countries where you have no legal entity, you cannot put them on payroll, and completion arrives long before an incorporation could. An Employer of Record employs them from day one, which closes a gap that otherwise leaves acquired employees unpaid and unsettled at exactly the wrong moment.
We employ people on your behalf across 214 countries and territories, including through acquisitions, divestitures and restructures where the legal entity does not yet exist.
Related reading: the benefits of mergers and acquisitions, the role of HR during M&A, and how to merge two teams into one.
Talk to our team about the transaction you are planning.
Vodafone's acquisition of Mannesmann in 2000, at around $180 billion, is generally regarded as the largest. Among those listed here, Verizon's $130 billion buyout of Vodafone's stake in Verizon Wireless is the biggest.
Google's purchase of Android for roughly $50 million in 2005, by a very large margin. Disney's $4 billion acquisition of Marvel is the strongest among the major deals.
Analysis generally points to consumer preferences moving away from packaged processed foods faster than the combined business adapted. The company subsequently wrote down billions in brand value.
No. AT&T fought a government challenge to complete the $85 billion deal in 2018, then divested the business in 2022, combining it with Discovery to form Warner Bros. Discovery.
Tens of thousands globally. Bloomberg Law recorded 48,833 in 2023, which was considered a subdued year by recent standards.
It varies by jurisdiction and by whether the businesses integrate. In cross-border deals the immediate question is whether the acquirer can legally employ them at all, which requires either a local entity or an Employer of Record.