Illumina Stock Falls Nearly 19% Despite Q3 EPS Beat and Raised Full-Year Guidance

Illumina shares plunged roughly 19% on October 30 after the genomics company reported Q3 2026 revenue of $1.13 billion, up 4.2% year over year but below Wall Street's consensus expectations, even as earnings per share beat estimates and the company raised its full-year outlook. The selloff was severe enough to rank Illumina among the worst-performing large-cap stocks on the day, alongside Intel, Reddit, and Roblox.

The revenue shortfall was partly distorted by a $37 million tariff refund that Illumina stripped out of reported revenue, intending to pass those savings on to customers. Excluding that adjustment, revenue came in at $1.17 billion, which cleared consensus. Non-GAAP diluted EPS was $1.44, and GAAP diluted EPS was $1.43, with the non-GAAP figure holding up even after excluding the tariff refund. The GAAP operating margin was 27.0%, while the non-GAAP operating margin excluding tariff refunds was 25.0%.

CEO Jacob Thaysen attributed the quarter to healthy clinical demand and strong NovaSeq X instrument placements. Despite that momentum, the company raised its full-year revenue guidance to a midpoint of $4.65 billion, roughly 0.6% above analysts' prior consensus, and lifted its full-year earnings guidance as well. Investors appear to have focused on the headline revenue miss and the fact that organic growth of just over 4% lags peers such as Thermo Fisher, which posted 6% organic revenue growth in its own third quarter and also raised guidance, suggesting the slowdown is specific to Illumina rather than sector-wide. The stock was trading at approximately 49 times forward earnings heading into the report, leaving little room for a top-line miss.