So, Senator Markwayne Mullin might be trading his seat in Congress for a big office at the Department of Homeland Security. President Donald Trump recently named the Oklahoma Republican as his pick to replace Kristi Noem. But before he potentially swaps committee hearings for security briefings, he was busy in the stock market.

Let's talk about what he bought and sold.

The February Trades: Health In, Tech and Auto Parts Out

According to data from government trades, Mullin made three moves on February 25. The headline grabber is a purchase: he bought between $50,000 and $100,000 worth of UnitedHealth Group (UNH) shares.

This isn't his first dance with the health insurance giant. He bought a smaller chunk last September, but had sold off a previous position just a month before that in August 2025. It's a bit of a back-and-forth relationship.

Here's where it gets interesting. Mullin currently serves on the Senate Committee on Health, Education, Labor and Pensions. He's also on subcommittees that deal directly with Health and Human Services and primary health. Buying stock in a massive health insurer while you help shape health policy? That's the textbook definition of a potential conflict of interest, and it's sure to come up when senators quiz him about his new job.

On the same day, he was also selling. He fully exited his positions in two other companies. He sold between $15,001 and $50,000 in Intuit (INTU) stock and between $50,001 and $100,000 in AutoZone Inc (AZO) stock.

The Intuit sale looks like it hurt. He had bought shares in December and September of 2025, and based on the stock's high prices on those purchase dates, he sold at a loss in February.

The AutoZone trade, however, was a winner. He originally bought shares back in October and September of 2023. By the time he sold on February 25, the stock was up more than 45% from the highest price he paid back then. Not a bad return for a holding of about two and a half years.

A History of Active Trading

These February trades are just the latest entries in a very busy portfolio. Mullin is known as an active trader on Capitol Hill.

He owns oil and defense stocks, sectors that have gotten a boost recently from geopolitical events. He's also been buying shares of smaller companies, which is less common for members of Congress who typically stick with big, stable names.

Speaking of big names, he's been actively buying up six of the seven so-called "Magnificent Seven" tech stocks, making some of his largest purchases in recent years on these market leaders.

The scale of his activity is significant. According to data from Quiver Quantitative, since 2023, Mullin has executed more than 500 stock trades involving over $24 million in total transaction value.

He hasn't always been perfect with the paperwork, either. In 2025, he was flagged for violating the STOCK Act—the law designed to prevent insider trading by Congress—by reporting transactions from 2023 a full two years late.

All of this history is now fair game. As Mullin goes through the confirmation process to become the Secretary of Homeland Security, his stock trading record is almost certainly going to be a topic of debate. Senators will want to know if his personal investments ever clouded his judgment or could influence his decisions on national security.

The political winds, however, might be at his back. With Republicans holding majorities in both the House and Senate, and a tradition of being accommodating to former colleagues in confirmation hearings, the path to approval for Mullin looks relatively clear. But first, he'll have to explain those trades.