Used 2021 GMC Sierra 3500HD for SaleNationwide

How much does the 2021 GMC Sierra 3500HD cost?

Prices have softened 7.11% compared to this time last year, making it a favorable time to shop this model year.

There are 737 listings available, which gives you a meaningful amount of inventory to compare.

Is the 2021 GMC Sierra 3500HD a good car?

Yes — 5/5 is a strong user rating for the 2021 GMC Sierra 3500HD. The overview points to a heavy-duty truck that combines serious work capability with a more polished feature set, plus broad cab, bed, and rear-axle choices that make it adaptable to different needs. It also offers strong towing and hauling numbers, along with useful tech and available safety features that make it easier to live with than a purely bare-bones work truck. With 34.3% of listings marked as good or great deals, you have some room to shop selectively.

Is the 2021 GMC Sierra 3500HD reliable?

Owners rate it 5/5, a strong signal of long-term satisfaction.

The overview suggests a truck built around capability, with a broad configuration range and available equipment that supports both work and daily use. Its available safety and driver-assist features also add confidence for used buyers who want a heavy-duty truck that feels more modern.

For long-term ownership, your biggest risk is buying a hard-used example that has been worked hard without proper maintenance or inspection.

What should I look for when buying a used 2021 GMC Sierra 3500HD?

Accident-free inventory is solid at 78.7% — always verify the vehicle history report.

You should prioritize a history report first, then focus on a thorough inspection of the truck’s condition, especially if it was used for towing or hauling. Pay close attention to signs of heavy-duty wear, uneven use, and any evidence that the truck’s capability may have been pushed hard. Because this model can be configured in many ways, matching the truck’s equipment and condition to your intended use matters just as much as the badge on the tailgate.

Is now a good time to buy a used 2021 GMC Sierra 3500HD?

This is a moderate, selective buyer’s market, so you can shop carefully and still find worthwhile opportunities.

• Deal availability: 34.3% of listings are priced as good or great deals.
• Inventory: There are 737 listings available.
• Price trend: Prices have softened 7.11% compared with last year.
• Clean inventory: 78.7% of listings are accident-free.

If you find a listing below $51,217, that's toward the low end of the year-round range and worth acting on quickly.

What is the 2021 GMC Sierra 3500HD's resale value?

The current average of $51,346 sits slightly below last year's $55,276.

That decline suggests the market has become a bit more favorable for buyers, but it also means future sellers may need to price competitively to stand out. If you buy well now, you may have a better chance of limiting depreciation pressure later. Strong condition and the right equipment mix should help your truck remain appealing when it is time to sell.

Vehicles with strong owner satisfaction ratings, like this model year's 5/5, tend to retain buyer demand, which supports resale value over time.

Should I buy a 2021 GMC Sierra 3500HD or consider a different year?

If you're weighing the 2021 against nearby model years, here's how to think about it:

Choose the 2021 if:

• 34.3% of listings are priced as good or great deals.
• Accident-free inventory is solid at 78.7% — always verify the vehicle history report.
• Price trend: Prices have softened 7.11% compared with last year.
• Owners rate it 5/5 — a strong satisfaction signal.

The bottom line: The 2021 is a strong choice if you want a heavy-duty truck with serious towing and hauling ability, a polished feature set, and a market that currently gives you some negotiating room. If you are especially price-sensitive, you may want to compare nearby years to see whether a lower-priced alternative gives you the equipment and condition you need without giving up too much capability.

How does the 2021 GMC Sierra 3500HD compare to the 2021 Ford F-350 Super Duty?

These recommendations are based on CarGurus' proprietary market data from October 27, 2026, CarGurus experts' opinions, and generative AI.