Used 2021 Mercedes-Benz GLS for Sale nearBoston, MA

How much does the 2021 Mercedes-Benz GLS cost?

Prices have softened 9.67% compared to this time last year, making it a favorable time to shop this model year.

There are 861 listings available, which gives you a solid pool of inventory to compare.

Is the 2021 Mercedes-Benz GLS a good car?

Yes — the 2021 Mercedes-Benz GLS earns a 4.7/5 user rating and an 8.3/10 expert rating. The model scores 9/10 across Look and feel, Performance, Technology, and Safety.

The overview positions it as a full-size luxury SUV that aims to bring S-Class-style refinement to a three-row format, and the test-drive summary backs that up with a higher standard of luxury, impressive performance, and spacious seating and cargo flexibility. That makes it a strong fit if you want a premium family hauler with flagship-style presence.

The trade-offs are clear: the third row is cramped, the technology can be unintuitive, and fuel economy is poor. If you value luxury, capability, and space more than efficiency or the easiest-to-use interface, it makes sense to keep this one on your shortlist.

36.9% of listings are priced as good or great deals, so there is meaningful market activity to shop from.

Is the 2021 Mercedes-Benz GLS reliable?

Owners rate it 4.7/5, a strong signal of long-term satisfaction.

The overview emphasizes a spacious, comfort-first three-row SUV, and the expert summary reinforces that it delivers on the S-Class-of-SUVs idea with a polished ride and strong luxury focus. The performance notes also point to a composed, capable chassis and multiple powertrain choices, which supports the sense that this is a well-engineered vehicle.

The performance content also highlights EQ Boost 48-volt mild-hybrid assistance across the lineup, which helps supplement power when needed. For used buyers, the main long-term ownership risk is that a complex luxury SUV can be costly to maintain if prior care was inconsistent.

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

Accident-free inventory is solid at 83.5% — always verify the vehicle history report.

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

Key things to evaluate:

• Trim level: The GLS is available in three levels: GLS 450, GLS 580, and the Mercedes-AMG GLS 63 performance model. 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 premium sound system. The GLS 580 adds V8 power, 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, quad-outlet exhaust, a chrome slotted grille, and a performance-inspired flat-bottomed steering wheel. The GLS 450 is the best-value trim if you want the core luxury and tech features without stepping up to the pricier V8 models.
• 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 come with Mercedes’ EQ Boost 48-volt mild-hybrid system, and the GLS 450 and GLS 580 route power through a nine-speed automatic transmission to 4MATIC all-wheel drive.
• Safety package: Standard safety 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 safety tech includes lane-keep assist, lane-change assist, adaptive cruise control, a following-distance indicator, and stop-and-go cruise control. Some advanced features are optional rather than standard.
• Infotainment: The GLS uses the MBUX infotainment system with a massive touch screen, a central controller, and touch-sensitive steering-wheel controls. It includes Apple CarPlay and Android Auto, but they require a USB-C cable connection. The system also supports voice control through “Mercedes” or “Hey Mercedes,” and the digital dash adds another layer of tech to learn.
• Fuel efficiency: The most-efficient variant returns 20 mpg city, 24 highway, 21 combined. The AMG GLS 63 returns 14 mpg city, 18 highway, 16 combined. The performance content also notes that the GLS 63 is a heavy SUV, which helps explain the efficiency trade-off.

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 trim to start with if you want the core GLS experience at the most approachable price. You still get the luxury basics, strong standard tech, and the full-size three-row layout, plus the best fuel economy in the lineup.
• GLS 580: This trim adds V8 power and a richer feature set, including heated-and-cooled front seats, massaging front seats, illuminated running boards, soft-close doors, and five-zone climate control. It suits you if you want more performance and comfort upgrades without going all the way to the AMG model.
• Mercedes-AMG GLS 63: This is the performance-focused choice, with the most aggressive styling and the strongest engine output. It makes sense if you want the most dramatic version of the GLS and are willing to accept the efficiency trade-offs.

Safety content notes that some advanced driver-assistance features are available rather than standard, so check the exact equipment on any used example.

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 deal activity to make timing matter.

• Deal availability: 36.9% of listings are priced as good or great deals.
• Inventory: There are 861 listings available.
• Price trend: Prices have softened 9.67% compared with last year.
• Clean inventory: 83.5% of listings are accident-free.

If you find a listing below $45,936, 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 $46,080 sits slightly below last year's $51,015.

That decline suggests the market has moved in buyers’ favor, which can make the GLS easier to purchase now but may also mean sellers need to price more competitively. If you own one and plan to sell later, the current trend points to a softer resale environment than a year ago.

Even so, the GLS still has the kind of luxury positioning and broad appeal that can help support demand among shoppers looking for a premium three-row SUV. Vehicles with strong owner satisfaction ratings, like this model year's 4.7/5, 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, 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 safety tech includes 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, but some of the more advanced driver-assistance features are still optional. If those systems matter to you, make sure the specific used vehicle you’re considering has them equipped.

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:

• 36.9% of listings are priced as good or great deals.
• Accident-free inventory is solid at 83.5% — always verify the vehicle history report.
• Price trend: Prices have softened 9.67% compared with last year.
• Owners rate it 4.7/5 — a strong satisfaction signal.
• The 2021 GLS stands out for its S-Class-style luxury, spacious seating, and impressive technology.

Consider the 2022 if:

• At $45,994, the 2022 costs less than the current year's $46,080 average.
• Mercedes withdrew most V8 models, leaving only the base six-cylinder GLS 450 4Matic.

The bottom line: If you want the broader 2021 lineup with multiple powertrain choices and strong market availability, the 2021 is the better all-around pick. If you are price-sensitive and only need the base six-cylinder experience, the 2022 can be the simpler, slightly cheaper path.

How does the 2021 Mercedes-Benz GLS compare to the 2021 BMW X7?

Expert Pros & Cons (per CarGurus review team)

2021 Mercedes-Benz GLS:

• Pros: Multiple powertrain options, Plenty of cargo space, Impressive technology.
• Cons: Cramped third row, Unintuitive technology, Poor fuel economy.

2021 BMW X7:

• Pros: Multiple powertrain options, Great handling, Powerful engine.
• Cons: Advanced safety features are not standard.

Our experts score the 2021 Mercedes-Benz GLS 8.3/10 and the 2021 BMW X7 7.7/10. The GLS leans harder into luxury, cargo space, and technology, while the X7 emphasizes handling and a powerful engine. If you want the more feature-rich, comfort-first choice, the GLS has the edge; if driving feel matters more, the X7 is the stronger alternative.

Read our full side-by-side expert comparison here.

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