ABOUT The Sullivan Group

Over 30 Years of Trust, Growth, and Personalized Service

With a legacy that began in Northern California and deepened in Southern California, The Sullivan Group has remained focused on one thing: helping individuals, families, and business owners make confident financial decisions. As fiduciary advisors, we uphold a standard of service rooted in trust, transparency, and long-term partnership.

Our story is defined by relationships, not transactions. We take the time to understand each client’s vision—then build tailored strategies that evolve alongside life’s milestones. Whether you're planning for retirement, managing a complex estate, or overseeing corporate finances, we offer clear direction through every financial stage.

What Drives Us

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Fiduciary Commitment

Your financial well-being is our sole priority. Every recommendation is made in your best interest—with no product quotas, no hidden agendas, and no pressure.

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California Roots, Broad Perspective

Originating in Northern California and now serving Southern California from Mission Viejo, we bring a regional understanding and a national lens to every plan.

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Team-Based Service Model

Collaboration is at the core of our approach. We work together—and alongside your tax and legal advisors—to provide a 360-degree strategy tailored to your needs.

Built for Lifelong Impact


As a boutique financial advisory firm, we focus on quality, not quantity. We build long-term relationships based on trust, not transactions—and we’re proud that most of our clients come to us by referral. Our mission is to simplify the complex, empower the informed, and be the steady voice through changing times.

Our Planning Process

How We Help You Move Forward—With Purpose

1. Discover

We begin by listening. Every new relationship starts with a deep conversation about your values, goals, and financial picture.

2. Analyze

Using our experience and industry tools, we build a clear understanding of your current position and identify key planning opportunities.

3. Implement

Together, we take action—applying proven strategies and aligning your plan with your evolving life and priorities.

4. Evolve

Life changes—and your financial plan should keep pace. We meet regularly, adjust as needed, and stay connected so nothing falls through the cracks.

Managing Director

Sean A. Lehmann

Sean re-established The Sullivan Group, with Partner Tom Sullivan, in 1994. With decades of experience at Morgan Stanley and Wachovia Securities, Sean now leads with a focus on retirement income strategies, charitable giving, and multi-generational planning. He’s also a veteran Naval Aviator and committed community volunteer.

Financial Advisor

Allison Peterson

Since joining in 2007, Allison has become a key advisor with a strong focus on client care. Based in South Orange County, she’s passionate about helping clients build plans that support both their long-term goals and day-to-day realities. She brings both insight and empathy to every conversation.

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Let’s Build Your Financial Future Together

Whether you're starting fresh or re-evaluating an existing plan, we're here to guide the way.

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