Stephen O'Sullivan
Account Executive · Customer Success Leader

Stephen B. O'Sullivan

Strategic Account Executive and Customer Success leader with 8+ years driving enterprise client growth, adoption, and retention across complex SaaS ecosystems. I manage multimillion-dollar portfolios, lead cross-functional initiatives, and build scalable enablement programs that accelerate revenue and customer value.

✉ Email me View experience
8+
years in SaaS & ad tech
$20M+
in portfolios led by my team
40%
lift in feature adoption
30%
faster new-hire ramp

Experience

From a 20-person startup to a 1,300+ person global platform. Tap any role for the details.

Company snapshot: MIT-founded startup of ~20 people. The entire sales team was two people: me and the head of sales.

  • Account Executive for a retail real estate analytics startup.
  • Responsible for net new logos and bringing in ARR through cold outbound, trade shows, and networks.

Company snapshot: a commerce analytics company of 100+ employees, acquired by SPINS in January 2026 (read the announcement).

  • Commercial lead for a portfolio of Fortune 1000 brands, owning renewals and retention through ValueSelling-driven, consultative engagements.
  • Worked global accounts and regularly prospected into EMEA and APAC through outbound email and calling.
  • Collaborated cross-functionally with Sales, Customer Success, and Product to align MikMak's commerce analytics solutions with client goals and drive measurable ROI.
  • Managed renewal forecasting and account health in Salesforce while engaging stakeholders across Marketing, eCommerce, and IT to secure long-term partnerships.

Company snapshot: I joined as employee #340, just as StackAdapt was expanding into the US. By the time I left, it had grown to 1,300+ employees and operated as a global company. It also raised $235 million in funding while I was there.

Manager of Client Services

January 2023 – April 2025
  • Led a team of 4 Account Managers managing Core portfolios worth $20M+, aligning strategy with OKRs and driving product adoption and client satisfaction.
  • Directed cross-functional initiatives across Product, Sales, and Support, including the rollout of 3+ major product releases and implementation playbooks.
  • Developed and facilitated training programs for new hires, reducing ramp-up time by 30%.
  • Acted as strategic advisor to top-tier clients, guiding onboarding and optimization of platform usage, resulting in a 20% lift in client retention.

Account Manager

April 2021 – December 2022
  • Owned the full customer lifecycle from onboarding to upsell, resulting in 25% YoY growth in portfolio revenue.
  • Delivered tailored product demos and strategic consultations, increasing feature adoption by 40%.
  • Used the Challenger Selling methodology to identify expansion opportunities, regularly exceeding targets.
  • Partnered with Product and Engineering to deliver client feedback, contributing to 2 key product enhancements.

Senior Programmatic Trader

December 2020 – March 2021

Programmatic Trader

August 2019 – November 2020
  • Managed multimillion-dollar campaigns across DSPs (DV360, The Trade Desk), optimizing to CPA and ROI targets.
  • Streamlined client reporting and transparency, increasing satisfaction scores.
  • Developed internal training that was adopted across the New York, Los Angeles, and Raleigh offices.
  • Launched and managed campaigns for Fortune 500 clients, ensuring flawless execution and optimization.
  • Translated media plans into actionable DSP strategies, collaborating with internal planning and creative teams.
  • Improved performance by proactively identifying and implementing campaign optimizations.
  • Partnered with technical teams to troubleshoot and enhance platform usability for enterprise users.
  • Used SQL to generate client-specific usage reports and identify trends in product performance.
  • Supported UAT sessions, gathering client feedback and contributing to product roadmap decisions.

Skills & Tools

Filter by area.

Enterprise renewals Net new logo prospecting Upsell & expansion Renewal forecasting ValueSelling Challenger Selling Customer onboarding Account health & retention Product adoption Strategic advisory Product demos Team leadership Training & enablement Cross-functional initiatives OKR alignment Implementation playbooks Salesforce DV360 The Trade Desk SQL Client reporting & analytics

Education

Saint Louis University, John Cook School of Business

Bachelor of Science in Business Administration · May 2017

Concentration in Economics and Business Analytics

St. Louis, MO

About me

My life is full of travel and adventure. Pick a season to see what I'm up to.

🏋️ All year

Outside of work, I'm usually at a CrossFit class during the week.

🥾 Fall

If it's fall, I'm hiking somewhere in New England.

🎿 Winter

If it's winter, I'm probably skiing somewhere in the world. Last year I spent a week skiing the Dolomiti Superski and completing the Sellaronda.

🏖️ Summer

In the summer, you can find me at a drive-on beach south of Boston or out on Cape Cod, enjoying some oysters.

☘️ Irish roots

My family is from Ireland, so I spend a lot of time going back to visit.

Favorite place
Kinsale, County Cork
Favorite ski resort
Palisades Tahoe
Favorite beach
Cahoon Hollow Beach
Favorite hike
Flume Gorge Trail
Favorite golf course
The Ledges of St. George

Let's talk

Introductions, questions, or opportunities: I'd love to hear from you.

✉ Stephen.o-sullivan@outlook.com