Used 2021 Mercedes-Benz GLS for Sale nearSaint Louis, MO

How much does the 2021 Mercedes-Benz GLS cost?

Prices have softened 11.86% compared to this time last year, making it a favorable time to shop this model year.

There are 807 listings available, which suggests you have a modest amount of inventory to compare.

Is the 2021 Mercedes-Benz GLS a good car?

Yes — the 4.67/5 user rating points to strong owner satisfaction, and the expert rating is 8.33/10. The model scores 9/10 across Look and feel, Performance, Technology, and Safety.

The 2021 Mercedes-Benz GLS is positioned as a full-size luxury SUV that aims to bring S-Class-style refinement to a three-row format. The expert test-drive summary emphasizes its higher standard of luxury, impressive performance, spacious seating, and cargo flexibility, so you’re looking at a premium family hauler with real utility.

The main trade-offs are a cramped third row and technology that can be unintuitive. Fuel economy is also a weak point, so this is best if you value comfort, space, and upscale presence more than efficiency.

With 39.3% of listings marked as good or great deals, there is a meaningful share of attractive pricing in the market.

Is the 2021 Mercedes-Benz GLS reliable?

Owners rate it 4.67/5, a strong signal of long-term satisfaction.

The GLS is described as a polished, comfort-first luxury SUV with a composed ride and strong overall execution. The expert test-drive notes also point to a hushed cabin and a vehicle that feels smaller and easier to maneuver than its size suggests, which supports confidence in day-to-day ownership.

Its performance hardware is substantial, with multiple powertrain choices and standard EQ Boost mild-hybrid assistance across the lineup. That kind of setup can be appealing for refinement, but it also means you should pay close attention to service history and how the vehicle has been maintained.

If you’re shopping used, the biggest long-term ownership risk is likely to come from complexity rather than basic durability, so a thorough pre-purchase inspection matters.

What should I look for when buying a used 2021 Mercedes-Benz GLS?

Accident-free inventory is solid at 83.6% — always verify the vehicle history report.

You should still check the vehicle history report carefully and prioritize a pre-purchase inspection, especially on a luxury SUV with advanced electronics and multiple available powertrains. Focus on overall condition, signs of heavy family use, and whether the technology and driver-assistance features work as intended.

Key things to evaluate:

• Trim level: The GLS 450 includes remote keyless entry, remote start, nine USB ports, dual-zone automatic climate control, heated front seats, a power liftgate, wireless device charging, Apple CarPlay, Android Auto, satellite radio, and a 13-speaker Burmester sound system. The GLS 580 adds V8 power plus heated-and-cooled front seats, massaging front seats, illuminated running boards, soft-close doors, and five-zone automatic climate control. The AMG GLS 63 adds more aggressive bodywork, a quad-outlet exhaust, and a performance-inspired cabin. The GLS 450 is the best-value starting point if you want the core luxury experience without stretching to the pricier variants.
• Powertrain: The GLS 450 uses a twin-turbocharged 3.0-liter inline-six with 362 horsepower and 369 pound-feet of torque. The GLS 580 uses a twin-turbocharged 4.0-liter V8 with 483 hp and 516 lb-ft. The AMG GLS 63 uses a hand-crafted 4.0-liter twin-turbo V8 with 603 hp and 627 lb-ft. All engines include EQ Boost 48-volt mild-hybrid assistance.
• Safety package: Standard equipment includes Active Brake Assist, forward-collision avoidance, rain-sensing wipers, blind-spot monitoring, automatic high beams, automatic parking assist, a surround-view camera system, a driver-drowsiness monitor, and crosswind assist. Available features include lane-keep assist, lane-change assist, adaptive cruise control, a following-distance indicator, and stop-and-go cruise control.
• Infotainment: The GLS uses the MBUX system with a massive touchscreen, a trackpad controller, Apple CarPlay, Android Auto, and voice control. The setup is feature-rich, but it can take time to learn.
• Fuel efficiency: The GLS 450 returns 20 mpg city, 24 highway, and 21 combined. The GLS 63 returns 14 mpg city, 18 highway, and 16 combined. In combined driving, the test vehicle averaged 15.3 mpg.

Which 2021 Mercedes-Benz GLS trim should I buy?

The 2021 Mercedes-Benz GLS is offered in 3 trim levels: GLS 450, GLS 580, and Mercedes-AMG GLS 63.

Here's the short version:

• GLS 450: This is the smartest starting point if you want the GLS experience at the lowest entry price. You still get a long list of standard luxury and tech features, including heated front seats, wireless charging, Apple CarPlay, Android Auto, and the Burmester audio system.
• GLS 580: This is the step-up choice if you want more power and more comfort features. The V8, massaging front seats, soft-close doors, and five-zone climate control make it the more indulgent pick.
• Mercedes-AMG GLS 63: This is the performance-focused choice, with the most powerful engine, more aggressive styling, and a sportier cabin. It makes sense if you want the most dramatic version of the GLS and are willing to pay for it.

Safety content notes that the GLS comes standard with a broad driver-assistance suite, while additional aids such as adaptive cruise control and lane-keep assist are available.

Is now a good time to buy a used 2021 Mercedes-Benz GLS?

This is a moderate market for selective buyers, with enough inventory to shop carefully and enough price softness to create opportunities.

• Deal availability: 39.3% of listings are priced as good or great deals.
• Inventory: There are 807 listings available.
• Price trend: Prices have softened 11.86% compared with last year.
• Clean inventory: 83.6% of listings are accident-free.

If you find a listing below $45,941, that's toward the low end of the year-round range and worth acting on quickly.

What is the 2021 Mercedes-Benz GLS's resale value?

The current average of $45,941 sits slightly below last year's $52,124.

That decline suggests the market has already adjusted downward, which can help you as a buyer but may limit upside if you plan to resell soon. For a future seller, the key takeaway is that pricing pressure has been real, so condition and equipment will matter a lot when it’s time to list.

Well-kept examples with desirable trims and strong feature content should hold up better than neglected ones. If you buy carefully now, you’re more likely to preserve value later.

Vehicles with strong owner satisfaction ratings, like this model year's 4.67/5, tend to retain buyer demand, which supports resale value over time.

Is the 2021 Mercedes-Benz GLS safe?

The 2021 Mercedes-Benz GLS earns a 9/10 safety score from our experts.

It comes standard with Active Brake Assist, forward-collision avoidance, blind-spot monitoring, automatic high beams, automatic parking assist, a surround-view camera system, a driver-drowsiness monitor, and crosswind assist. Available upgrades include lane-keep assist, lane-change assist, adaptive cruise control, a following-distance indicator, and stop-and-go cruise control.

That gives you a strong standard safety foundation, though some of the more advanced driver aids are optional rather than standard. If safety tech is a priority, you’ll want to confirm exactly which package a used example has before you buy.

Should I buy a 2021 Mercedes-Benz GLS 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:

• 39.3% of listings are priced as good or great deals.
• Accident-free inventory is solid at 83.6% — always verify the vehicle history report.
• Price trend: Prices have softened 11.86% compared with last year.
• Owners rate it 4.67/5 — a strong satisfaction signal.
• The 2021 GLS offers multiple powertrain choices, spacious seating, and impressive technology.

Consider the 2022 if:

• At $46,509, the 2022 costs more than the current year's $45,941 average.
• Mercedes simplified the lineup to the base six-cylinder GLS 450 4Matic.

The bottom line: If you want the broader 2021 lineup with more trim and powertrain choice, the 2021 is the better buy. If you’re focused on the newest nearby model year and don’t mind paying a bit more for a simpler lineup, the 2022 is the cleaner alternative. For price-sensitive shoppers, the 2021’s softer pricing makes it the more compelling value play.

These recommendations are based on CarGurus' proprietary market data from October 6, 2026, CarGurus experts' opinions, and generative AI.