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Black Twenty One

5 ★★★★★ 29 Google reviews · Kickboxing gym in Denver, Colorado

Free trial Beginners welcome Kids & teens Cardio kickboxing Competition team

Plan your first class

  • Free trial or intro class most gyms welcome new members with a free trial or intro class — check their site or give them a call to book your first session
  • Beginner-friendly all fitness levels welcome, including total beginners — no experience needed, and you get in shape by training, not before
  • Cardio kickboxing classes high-energy cardio kickboxing on the bags and pads — a fun, sweaty workout built for fitness and weight loss, at your own pace
  • Kids & teen classes kids and teen kickboxing classes — built around confidence, focus, and fun
  • Competition team a competition team for members who want to test themselves in the ring — amateur kickboxing, muay thai, or K-1
  • Today see hours ·
  • Website & schedule blacktwentyone.com — book classes and see the live schedule
  • Phone (720) 935-1872

Hours

Monday 5:45–8 AM, 5:30–8 PM
Tuesday 5–8 PM
Wednesday 5:30–9 AM, 5:30–8 PM
Thursday 5:30–7:30 PM
Friday 5:30 AM–12 PM
Saturday 7:30 AM–1 PM
Sunday Closed

Hours shift for holidays and class-schedule changes — worth a quick check before a special trip.

The classes they run

Kickboxing classes on the schedule at Black Twenty One, confirmed in members' own reviews and the gym's own info — not guessed from the sign out front.

🔥 Cardio Kickboxing 6 mentions

“You will leave confident and sweaty, like every great workout should leave you.”

All gyms that run cardio kickboxing →

🌱 Beginners 7 mentions

“Alejandro is very patient especially with someone like me who had no experience and who might take a little longer to learn the proper technique and correct combinations.”

All gyms that run beginners →

🏆 Competition Team

“Whether you’re looking to compete or just get in shape, I highly recommend Coach Alejandro and his gym.”

All gyms that run competition team →

🥊 Boxing 15 mentions

“The level of instruction in both boxing and kickboxing is top-notch you truly learn proper technique, from solid offensive combinations to strong defensive fundamentals.”

All gyms that run boxing →

Other martial arts here

Kickboxing gyms are usually multi-discipline. Here's what else members mention training under the same roof at Black Twenty One — mined from their reviews and the gym's own info.

🥊 Boxing 15 mentions

“The level of instruction in both boxing and kickboxing is top-notch you truly learn proper technique, from solid offensive combinations to strong defensive fundamentals.”

Other gyms that also teach boxing →

Disciplines are mined from reviews and the gym's own info — they show what members have trained, not a formal class guarantee. If you specifically want muay thai, boxing, or MMA alongside your kickboxing, confirm the current schedule with the gym.

What members say

The things reviewers bring up again and again across 29 Google reviews — in their own words.

🧑‍🏫 expert, motivating coaching 7 mentions

“Alejandro is a great coach, breaks everything down step by step and brings out the best in people.”

🌱 welcoming to beginners 8 mentions

“Alejandro is very patient especially with someone like me who had no experience and who might take a little longer to learn the proper technique and correct combinations.”

🎉 fun, high-energy classes 8 mentions

“You will leave confident and sweaty, like every great workout should leave you.”

💦 killer cardio workout 6 mentions

“You will leave confident and sweaty, like every great workout should leave you.”

🏆 active competition / fight team 2 mentions

“He’s cornered me for multiple fights, always bringing a calm and supportive presence.”

💵 good value / fair pricing 3 mentions

“One last part (maybe the most important) is his gym is very affordable for everyone to join.”

From the reviews

I’ve been going here for a year. I’ve improved my stretching, balancing, hand / eye coordination, core strength and most importantly, my confidence and physique in boxing. I also take private lifting / boxing sessions to improve my footwork, speed, and power. Incredible community.

★★★★★ — Ajay, Jan 2023

I’ve been a part of many gyms and been to many work out classes but this one takes the cake. Alejandro has done an incredible job of creating a fun safe environment to learn and grow as well as a place to push yourself without being afraid to fail.

★★★★★ — Jess, Dec 2022

Highly recommend! In a sea full of outrageous prices, this one stands out. Incredible rates and intense & doable workouts (for all levels of fitness). If you want to lose weight, get fit or actual learn to fight (boxing and/or kickboxing) this is the gym for you!! Alejandro always brings it, every class.

★★★★★ — Steph, Jul 2021

Alejandro is the best trainer I’ve ever had. I’d never done kickboxing before. I can now say I’m sold for life. I don’t think I’ve ever done the same routine twice. His workouts are ever changing and completely addictive. I literally leave there dripping sweat every time.

★★★★★ — Ashley, Feb 2021

Excerpts from public Google reviews. Read all 29 reviews →

New to kickboxing? Start at Black Twenty One

Black Twenty One comes up as a beginner-friendly gym — noted on their own site. If you've never thrown a punch or a kick, that's exactly who a good beginners class is for. A few things worth knowing before your first week. First, you don't need to be fit or coordinated to start — you get in shape by training, not before it, and coaches scale every drill to you. Second, you won't be thrown into hard sparring — reputable gyms build the basics (stance, footwork, and punches and kicks on pads and bags) first, and any contact eases in gradually under a coach's control. Third, all fitness levels really are welcome — ask about a dedicated beginners or fundamentals class time so your first session is alongside others who are also starting out. Most gyms are happy to let you watch or try a class first, so reach out before you commit.

Check beginner classes on their site

Your first kickboxing class at Black Twenty One

Nervous about walking into a kickboxing gym for the first time? Almost everyone is, and good coaches expect beginners to come through the door. Here's what to know. What to expect: a typical first class is a warm-up, then drilling the basics — stance, footwork, and punches and kicks on pads or a heavy bag — not hard sparring. Go at your own pace and rest whenever you need to; no one will bat an eye. What to wear: comfortable athletic clothes you can move and sweat in, and supportive trainers. What to bring: water, and hand wraps and gloves if you have them — many gyms lend loaner gloves for a first class, so it's worth asking when you call. As you keep training you'll add your own gloves and wraps (and shin guards once you start sparring). Sparring is optional and eases in gradually, once your basics are solid. Arrive 10–15 minutes early to sign a waiver and meet the coach. It gets easier fast — most people feel far more at home by their third class.

Kickboxing is a contact sport. Warm up, pace yourself, listen to your coaches, and if you have any injuries or health concerns, mention them before class and check with a doctor if you're unsure.

Where to find Black Twenty One

1870 S Acoma St, Denver, CO80223

Get directions Instagram

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Listing verified July 2026 from public business records and member reviews. Something out of date? Report a correction. Own this gym? Claim your listing — it's free.