Marvell Technology shares are rebounding quickly. The stock rose 8.4% in premarket trading on Monday after S&P Dow Jones Indices said Friday evening that Marvell will join the S&P 500 on June 22 during the index’s quarterly rebalancing. The news came just hours after Marvell dropped 17% in one of the semiconductor sector’s toughest sessions this year. Here’s what the index addition could mean for the stock and why Friday’s selloff might have been too harsh.
Joining the S&P 500 often gives stocks a short-term boost. Funds that track the index must buy shares of new companies, creating steady buying pressure. Marvell was already up 210% for the year through Friday, thanks to strong demand for its networking chips and optical parts from AI data center operators. Being added to the index brings in another big buyer for a stock that was already doing well.
Friday’s drop in Marvell’s stock happened because the whole sector was down, not because of any Marvell-specific news. Broadcom gave weaker revenue guidance than expected, and a strong May jobs report led investors to pull back from semiconductor stocks. The iShares Semiconductor ETF fell 10% on Friday but recovered 4.9% on Monday.
Flex shares are also up on Monday, rising 4.3% in premarket trading after gaining 151% in 2026, helped by a surge in data center construction. Flex will join Marvell in the S&P 500 on June 22. Both companies will replace Campbell’s, a canned foods maker, and Pool, a swimming pool supplier, in the index. On Monday, Campbell’s fell 0.8% and Pool dropped 0.3% in premarket trading.
