401(k) Balances Soar to Record High, Driven by Boomers and Millennials Fidelity reports a 10.5% quarterly increase in average 401(k) balances, reaching $155,800. Baby boomers hold the largest average balance at $283,200, while millennials see the fastest growth with a 14.3% rise to $94,300. The boost is attributed to both market gains and steady contributions, though experts caution that true retirement readiness requires ongoing savings and employer matching - not just high balance snapshots. Americans' 401(k) balances reached a record high in the second quarter of 2026, with baby boomers leading in savings and millennials showing significant growth, according to Fidelity data. The average balance increased 10.5% to $155,800, driven by strong investment performance and steady contributions despite rising living costs. However, experts warn that record balances alone do not guarantee sufficient retirement preparedness - consistent saving and employer matching remain critical for long-term financial security