Willett Advisors LLC

What Willett Advisors LLC does

Willett Advisors LLC is a private single-family office headquartered in New York that manages the philanthropic assets of Michael R. Bloomberg, including the assets of Bloomberg Philanthropies. Founded in 2010 and operating with a lean team of 1-10 employees, the firm employs a flexible investment approach aimed at long-term capital appreciation through a diversified portfolio. Its stated asset class coverage spans public markets, hedge funds, private equity and credit, real assets, and direct investments, executed both through selected third-party managers and direct positions — a structure typical of large endowments, foundations, and family offices.

The firm's go-to-market is structurally non-commercial: there is no external product offering, no fee schedule, no marketing beyond a corporate website, and no public revenue or AUM disclosure. Its investment activity is observed through disclosed direct-investment participation, most notably a co-investor role in Kinaset Therapeutics' $103 million oversubscribed Series B financing in January 2026 to advance frevecitinib, an inhaled pan-JAK inhibitor for severe asthma. Leadership is led by Chairman and CEO Steven Rattner, with Brian Allen as Managing Director of Private Equity and Olivia Ouyang as Managing Director.

Because Willett serves a single principal, there is no customer segmentation in the conventional sense and no disclosed pricing model. Revenue mechanics are not applicable in a fee-based sense; economic output is realized through investment performance on the philanthropic capital it stewards. The firm operates as an independently managed LLC with no disclosed parent company or institutional investors.

Name

Willett Advisors LLC

Legal name

Willett Advisors LLC

Website

http://www.willettadvisors.com

Company type

Private

Founded year

2010

Operating status

Operating

Headcount range

1–10 employees

Short description

Willett Advisors LLC is a private New York-based family office that manages the philanthropic assets of Michael R. Bloomberg, including Bloomberg Philanthropies, deploying capital across public markets, hedge funds, private equity, real assets, and direct investments.

Ownership category

akta.pro rank

Product category

Family Office Investment Management

NAICS

Portfolio Management and Investment Advice (52394), Portfolio Management and Investment Advice (523940)

SIC

Investment Advice (6282)

akta.pro primary industry

Portfolio Construction & Asset Allocation Advisory (FSAEAAAC)

akta.pro secondary industry

Real Estate Portfolio & Fund Management (Institutional/REIT/PE) (BPAJAMAJ)

Keywords

• Philanthropic asset management
• Family office investing
• Diversified portfolio management
• Private equity investments
• Endowment-style investing

Headquarters

HQ city

New York

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Services

Marketing channels1 record

Core offering

Willett Advisors LLC manages the philanthropic assets of Michael R. Bloomberg, including the assets of Bloomberg Philanthropies. The firm pursues long-term capital appreciation by constructing a diversified investment portfolio, investing both through selected third-party managers and directly across a broad range of asset classes including public markets, hedge funds, private equity and credit, real assets, and direct investments.

Product overview

Willett Advisors LLC is a single family office entity that manages the philanthropic assets of Michael R. Bloomberg, including the assets of Bloomberg Philanthropies. The firm operates as a unified investment management organization rather than a product-based company. It employs a flexible approach to achieve long-term capital appreciation through a diversified investment portfolio, historically focusing on public markets, hedge funds, private equity and credit, real assets, and direct investments. The firm manages assets both through selected third-party managers and directly.

Differentiator

Problem solved

Functional benefit

Products and services

• Philanthropic Asset Management Discretionary investment management of the philanthropic assets of Michael R. Bloomberg, including the assets of Bloomberg Philanthropies. Delivered via a diversified portfolio across public markets, hedge funds, private equity and credit, real assets, and direct investments, executed through selected third-party managers and direct allocations.

Segments1 record

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Scale indicators1 record

Recent moves1 record

Expansion highlights1 record

Direct peers

• Emerson Collective: Laurene Powell Jobs's family office/philanthropic vehicle pursuing mission-aligned direct investments across asset classes, blending philanthropy and principal capital allocation.
• BDT & MSD Partners: Advisory and merchant-banking firm serving founders and ultra-wealthy families with multi-asset strategies including direct investments — comparable in principal alignment and direct-deal participation.
• Rockefeller Capital Management: Multi-family office and wealth manager for ultra-high-net-worth families with diversified portfolio mandates — comparable in client base, scale, and advisory scope.
• Hillspire LLC: Jeff Bezos's family office, executing a diversified allocation across public and private markets for one principal — directly analogous in structure to Willett.
• Bessemer Trust: Multi-generational wealth advisor for ultra-high-net-worth families with multi-asset portfolio mandates — comparable in client profile and advisor role.
• Cambridge Associates: Endowment and foundation investment advisor running multi-asset portfolios for institutional-style principals — Willett's 'similar to endowments, foundations and family offices' framing maps directly.
• Iconiq Capital: Multi-family office and wealth manager to tech founders and executives with diversified multi-asset advisory mandates — strong peer for portfolio construction and direct-deal access.
• Soros Fund Management LLC: George Soros's family office investing across a broad, opportunistic multi-asset mandate — comparable in scale, flexibility, and principal-driven governance.
• Cascade Investment LLC: Bill Gates' investment vehicle — a single family office managing a diversified multi-asset portfolio for an ultra-high-net-worth principal, with comparable scope and flexibility.

Broad incumbents

• Angelo Gordon (TPG): Large alternative-investment manager running multi-strategy mandates including credit and real assets — overlaps with Willett's hedge, credit, and real-asset sleeve from an external manager perspective.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat3 records

Key risks6 records

Key highlights6 records

Customer concentration

• LinkedInlinkedin.com/company/willett-advisors-llc

Revenue estimate

Valuation estimate

Number of profiles

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments20 records

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Willett Advisors LLC