The deal highlights Aon's efforts to further expand its presence in the vast and fast-growing U.S. middle-market insurance segment, which caters to mid-sized businesses.
The U.S. middle-market segment is pegged at more than $40 billion and accounts for more than one-third of U.S. commercial property and casualty direct written premiums.
The USI deal builds on Aon's $13 billion acquisition of middle-market property and casualty broker NFP in 2024 and will add heft to its health, talent and human capital advisory offerings.
"USI will substantially enhance our middle-market footprint and expand access for our firm in the E&S (excess & surplus) segment," Aon CEO Greg Case said. The E&S segment is among the fastest-growing areas in U.S. commercial insurance.
Aon shares fell 1.8% premarket. The stock is flat this year through last close.
Founded in 1994, USI is an insurance brokerage and consulting firm which offers property and casualty, employee benefits, personal risk, program and retirement services. It began with a single office and has since scaled into the tenth largest U.S. insurance brokerage with about $3 billion in annual revenue.
Other recent mega deals in the insurance brokerage sector include Arthur J. Gallagher's AJG.N $13.5 billion acquisition of AssuredPartners and Brown & Brown's BRO.N nearly $10 billion purchase of Accession Risk Management, both finalized last year.
Aon, one of the world's largest insurance brokers, caters to clients in over 120 countries, helping them navigate increasing complexity and volatility.
The USI deal is expected to close in the fourth quarter of 2026 and anticipated to boost Aon's adjusted profit in 2028. Aon plans to fund the deal through debt and doesn't expect near-term share buybacks as it prioritizes debt repayment.
USI CEO Mike Sicard will serve as Aon's president and global CEO of its middle-market platform.
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