John Brennan
InvestorManaging Partner at Holly Ventures
San Francisco Bay Area
Writes $200K – $5M checks · typically $2M
About
John Brennan founded and manages Holly Ventures, focusing on supporting early-stage cybersecurity entrepreneurs. He previously worked at YL Ventures, DCVC, OCA Ventures, and Horsley Bridge Partners, and holds an MBA from the University of Chicago and a BS from Trinity College in Connecticut.
Invests in
AI & Machine LearningCybersecurityDeveloper ToolsEnterprise SoftwareSaaS
Experience
- Holly VenturesFounder & Managing Partnercurrent2024 — presentSan Francisco Bay Area
- GlowSeed Investorcurrent2025 — present
- AsteliaSeed Investorcurrent2025 — present
- Beacon SecuritySeed Investorcurrent2024 — present
- VeniceSeed Investorcurrent2024 — present
- MINDSeed Investor2023
- Miggo SecuritySeed Investor2023
- GutsySeed Investor2022 — 2023
- Spera SecuritySeed Investor2022 — 2023
- Aim SecuritySeed Investor2022 — 2023
- Opus SecuritySeed Investor2022 — 2023
- Eureka SecuritySeed Investor2021 — 2023
- Valence SecuritySeed Investor2021 — 2023
- PiianoSeed Investor2021 — 2023
- Grip SecuritySeed Investor2021 — 2023
- enso.securitySeed Investor2020 — 2023
- CycodeSeed Investor2019 — 2023
- SatoriSeed Investor2019 — 2023
- Orca SecuritySeed Investor2019 — 2023
- Hunters.AISeed Investor2018 — 2023
- Vulcan CyberSeed Investor2018 — 2023
- Ride VisionSeed Investor2018 — 2023
- YL VenturesSenior Partner2017 — 2023San Francisco Bay Area
- Karamba SecuritySeed Investor2017 — 2023
- MedigateSeed Investor2017 — 2022
- build.security (acquired by Elastic)Seed Investor2020 — 2021
- AxoniusSeed Investor2017 — 2021
- Data CollectiveChief of Staff to Bradford Cross2016San Francisco Bay Area
- OCA VenturesInvestor2016Greater Chicago Area
- Horsley Bridge PartnersInvestment Associate2013 — 2015San Francisco Bay Area
- AccentureConsultant2010 — 2013Boston, MA.
- Merrill LynchWealth Management Intern2008Greater Hartford
- UBSWealth Management Intern2008Greater Hartford
Skills & more
Venture Capital51Entrepreneurship30Start-ups26Investments9Valuation12Financial Modeling23Private Equity11Due Diligence12Analytics9Corporate Finance6Economics5Financial Analysis4
+4 more
Business OperationsManagementLeadershipStrategyFrom John's professional profile.
Deals · 5
AsteliaSolo GP
via Holly Ventures · filed Feb 2026
BeaconSolo GP
via Holly Ventures
CiderSolo GP
via Holly Ventures
TalononeSolo GP
via Holly Ventures
VeniceSolo GP
via Holly Ventures
Attribution from SEC filings, press coverage, and firm rosters. Some rows are inferred. Not right? Tell us.
Frequently asked questions
- Who is John Brennan?
- John Brennan founded and manages Holly Ventures, focusing on supporting early-stage cybersecurity entrepreneurs. He previously worked at YL Ventures, DCVC, OCA Ventures, and Horsley Bridge Partners, and holds an MBA from the University of Chicago and a BS from Trinity College in Connecticut.
- Where does John Brennan work?
- John Brennan is Managing Partner at Holly Ventures.
- What does John Brennan invest in?
- John Brennan invests in AI & Machine Learning, Cybersecurity, Developer Tools, Enterprise Software, SaaS.
- What check size does John Brennan write?
- John Brennan typically writes checks of $200K – $5M.
- Where did John Brennan go to school?
- John Brennan studied at The University of Chicago Booth School of Business (Master of Business Administration (MBA), Entrepreneurship & Finance); Trinity College-Hartford (BS, Economics); St. Sebastian's.
Same school
Also attended The University of Chicago Booth School of Business698
Prashant ShahPartner at Monta Vista CapitalNoorPartner at Clear VenturesTinaInvestments & Portfolio Services Team Member at Clear VenturesKatrin GeyskensExecutive Director at Capricorn Venture PartnersBill PescatelloInvestor at LightbankGlebFounder and Managing Partner at iTech Capital
+ 692 more
Also attended Trinity College-Hartford69
Robert BibowManaging Partner at Parkway Venture CapitalSunil ChhayaFounder at Kearny JacksonLouis SchotskyManaging Partner at Navitas CapitalDouglas McadamsAdvisor - Ex. Navy Nuke at Balerion Space VenturesAlan GlassPartner — Co-Head of Endurance at Energize VenturesTracy ChadwellFounding Partner at 1843 Capital
+ 63 more
