Justin Zeefe is a Founding General Partner of Green Flag Ventures, the leading US-based venture capital firm investing in early-stage, internationally-scalable Ukrainian tech product startups in dual-use, AI, and cyber. Zeefe also founded the Ukraine Defense Investors Network, a chapter of the European Defense Investors Network – platforms connecting investors with one another and groundbreaking Ukrainian defense technology startups.
Prior to Green Flag, Justin co-founded and led Nisos – a leading managed intelligence firm protecting 20+ F500 enterprises against advanced digital threats, disinformation, and platform abuse. Under his leadership, Nisos scaled rapidly, reaching a valuation of $150 million post-Series B (still growing!).
Before launching Nisos, Justin served a decade in the U.S. Government, specializing in countering sophisticated, state-sanctioned digital adversaries. He served five years in Europe, with tours in both Iraq and Afghanistan. He began his career as an attorney before transitioning into roles combining national security expertise with technology-driven venture investment.
Justin is a mentor with Techstars, an advisor to NATO DIANA (Defence Innovation Accelerator), guiding founders building innovative companies in defense and emerging technologies. He frequently speaks and advises on cybersecurity, frontier-market investments, and defense innovation.
Beyond his professional commitments, Justin was a longtime volunteer EMT in DC and Maryland and he speaks mediocre German. Currently he is the third worst coach in his 9yo son’s soccer league.