Why Did Costco Stock Fall Today? Because It Had ‘Little Room for Error'

Costco shares fell on Thursday after the retailer’s June sales fell short of Wall Street’s high expectations. Shares have slid nearly 20% since setting an all-time high in May but still trade at a premium to Costco’s closest competitor, Walmart, and most other retailers.

Costco fell victim to its own excellence. The warehouse club on Wednesday evening said net sales grew 10.6% in June, its slowest pace since February. That was its first month-over-month deceleration in 2026: Sales growth accelerated every other month this year, rising from about 9% in January to more than 14% in May. Comparable sales grew 8.8%, fast for a national retailer with $250 billion in annual sales, but a slowdown from 12.5% in May.

Costco ( COST ) stock was down about 5% in recent trading, deepening a two-month slump that has shares trading about 17% below the record high they set in mid-May.

Costco’s sales and stock rose earlier this year as soaring fuel prices encouraged consumers to prioritize value when shopping. Shares—and now sales—have lost that momentum as oil prices have fallen in the past two months. Even so, shares are up about 6% since the start of the year, thanks in part to a strong start.

The S&P Consumer Staples Sector Index fell nearly 10% during the first weeks of the war in Iran as investors debated the impact soaring oil and gas prices would have on consumer spending. But Costco stock, trading near an all-time high when the war began, declined less than 5%, buoyed by the retailer’s membership model, low prices, and the boost to its gas station sales from soaring fuel prices. Investors began to sour on the shares in mid-May when the U.S. and Iran made progress toward a peace deal, undercutting some of the concerns that had supported shares, and traders p...