Insurance Brokerage Mega-Deals: Gallagher, Aon, Marsh, and Brown & Brown

Introduction

The insurance brokerage industry experienced the most concentrated period of mega-deal activity in its history between late 2023 and mid-2025. Four transactions totaling over $44 billion in aggregate value transformed the competitive landscape: Gallagher-AssuredPartners ($13.5 billion), Aon-NFP ($13 billion), Brown & Brown-Accession ($9.8 billion), and Marsh McLennan-McGriff ($7.75 billion). Unlike bank M&A, which is driven by regulatory capital and deposit franchise economics, insurance brokerage consolidation is driven by the EBITDA multiple arbitrage between small agencies (4-5x) and institutional platforms (14-17x), PE portfolio exit timing, and the structural advantages of scale in a fragmented industry. For FIG bankers, these transactions represent some of the largest advisory mandates in the FIG deal flow universe.

Gallagher-AssuredPartners ($13.5 billion, announced December 2024, closed August 2025) is the largest insurance brokerage acquisition ever. Arthur J. Gallagher acquired AssuredPartners, a PE-backed platform (GTCR and Apax Partners) with $2.9 billion in trailing revenue, approximately 10,900 employees, and over 400 offices across the US, UK, and Ireland. The valuation of 14.3x pro forma EBITDAC (net 11.3x after a $1 billion deferred tax asset) reflected AssuredPartners' position as a fully scaled platform that had already completed over 500 tuck-in acquisitions. The deal received an FTC second request in March 2025, extending the timeline by five months, but ultimately closed without forced divestitures or remedies.

EBITDAC

EBITDAC (Earnings Before Interest, Taxes, Depreciation, Amortization, and Change in Contingent Consideration) is the primary profitability metric for insurance brokerages. It adjusts standard EBITDA for changes in the fair value of contingent consideration (earn-outs) from prior acquisitions, which are a recurring feature of roll-up platforms that acquire dozens to hundreds of agencies annually. EBITDAC is the denominator in insurance brokerage valuation multiples (EV/EBITDAC), functioning analogously to how EV/EBITDA is used in corporate M&A. For large public brokers like Gallagher, Aon, and Marsh, EBITDAC margins typically range from 30-35%, reflecting the capital-light, fee-based business model where the primary cost is compensation for producers (brokers who originate and manage client relationships).

Aon-NFP ($13 billion, announced December 2023, closed April 2024) was the first mega-deal to close and the catalyst for the wave. Aon acquired NFP Corp, a middle-market property and casualty, benefits, wealth management, and retirement advisory platform with over 7,700 employees. The consideration comprised approximately $7 billion in cash and assumed liabilities plus $6 billion in equity (19 million Aon shares). NFP operates as an "independent and connected" platform, completing 27 middle-market acquisitions in 2024 alone. The deal is expected to be dilutive to EPS in 2025, break even in 2026, and become accretive in 2027 and beyond, with 6% organic growth achieved in 2025.

Brown & Brown-Accession ($9.8 billion, announced June 2025, closed August 2025) added the Accession Risk Management Group (parent of Risk Strategies and One80 Intermediaries) to Brown & Brown's franchise. The combined entity incorporates over 5,000 insurance professionals and $1.7 billion in pro forma 2024 adjusted revenue. Risk Strategies joins Brown & Brown's retail segment, while One80 Intermediaries joins a newly created specialty distribution segment, reflecting the strategic importance of wholesale and MGA channels.

Marsh McLennan-McGriff ($7.75 billion, all cash, announced September 2024, closed November 2024) added McGriff Insurance Services (an affiliate of TIH) with $1.3 billion in trailing twelve-month revenue and approximately 3,500 employees. Marsh described the deal as "modestly accretive" in year one and "meaningfully accretive" in year two and beyond. McGriff enhances Marsh's commercial property and casualty, employee benefits, management liability, and personal lines capabilities.

Three forces converged to produce this unprecedented concentration of mega-deals.

PE portfolio exits reached critical mass. AssuredPartners, the largest target, was a PE-backed platform where GTCR and Apax Partners had invested over a decade in building a $2.9 billion revenue franchise through 500+ acquisitions. The platform had reached a scale where further tuck-in acquisitions generated diminishing marginal returns relative to the platform's size, and the PE sponsors needed liquidity. Gallagher, as a strategic buyer with a 100+ deal-per-year acquisition machine, was the natural exit partner. GTCR realized 3x+ returns from its 2019 recapitalization. Similar dynamics applied to the other targets: NFP was backed by Madison Dearborn Partners, and Risk Strategies had PE backing. The 2024-2025 window offered favorable conditions (strong insurance market, low credit losses, willing strategic buyers) for PE exits at premium multiples.

Market share pressure from PE-backed consolidators. The rise of PE-backed platforms like Hub International ($29 billion valuation), Acrisure ($23 billion), and Alliant ($4.97 billion revenue) had eroded the public brokers' competitive position. Unique buyers in the brokerage market dropped from 140 in 2020 to 99 in the first half of 2025, reflecting consolidation among acquirers. The top 10 most active buyers increased their share of total deals from 44% in 2020 to 54% in 2025. The mega-deals were a strategic response: reclaim market share through transformational acquisitions rather than competing agency-by-agency against PE platforms with higher leverage tolerance and faster decision-making.

Scale advantages in compliance and technology. State-by-state licensing, surplus lines tax filings, fiduciary mandates, and cybersecurity requirements create disproportionate compliance costs for mid-market firms. Larger platforms automate these workflows across thousands of accounts, achieving structural cost advantages. Data analytics, AI-driven placement optimization, and digital client portals similarly benefit from scale, as the fixed investment is spread across a larger revenue base.

The mega-deals have significantly consolidated the top of the market. Marsh McLennan leads globally at $24.5 billion in revenue (its 15th consecutive year at the top), followed by Aon at $13.4 billion and Gallagher at approximately $14 billion post-AssuredPartners (up from $9.9 billion pre-deal). The top five players now control approximately 52% of the US insurance brokerage market.

The competitive implications extend beyond the mega-deal participants. Mid-market brokers (those with $50 million to $500 million in revenue) face a strategic decision: grow aggressively through PE-backed acquisition to reach defensible scale, or sell to a larger platform while valuations remain elevated. The number of independent mid-market brokers is declining as the industry bifurcates between global platforms and small local agencies, with the middle tier being absorbed in both directions.

Each mega-deal presents distinct integration challenges. Gallagher estimated $500 million in integration costs over three years (including $200 million in non-cash retention awards) and plans to increase its acquisition pace to 100+ deals per year post-close, nearly double its prior 50-60 annual pace. Aon's NFP integration deliberately preserved NFP's operational independence (the "independent and connected" model) to avoid disrupting the middle-market culture that drives organic growth and producer retention.

The talent retention challenge is significant. Insurance brokerage is a relationship business where top producers generate disproportionate revenue. Large-scale acquisitions risk prompting departures to independent firms or competitors, particularly if producers perceive reduced autonomy or unfavorable compensation changes. The $200 million in retention awards Gallagher committed to reflects the recognition that human capital, not physical infrastructure, is the primary asset being acquired.

The insurance brokerage mega-deal wave is the most visible example of a broader pattern in FIG M&A: capital-light, fee-based financial services businesses attracting transformational deal activity driven by scale economics, PE exit dynamics, and the structural attractiveness of recurring revenue streams. The advisory mandates generated by these transactions (sell-side for PE sponsors, buy-side for strategic acquirers, fairness opinions, antitrust advisory) are among the most lucrative in the FIG banker's toolkit.