$49 Cheap flight deals from St. Louis (STL) to Boulder (DEN)

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This Weekend's Flight Deals from St. Louis to Boulder

This weekend's flight prices found within the past 7 days, for the period specified. Prices and availability are subject to change. Additional terms apply.

Sun, Aug 2 - Sat, Aug 8
STL
Lambert-St. Louis Intl.
DEN
Denver Intl.
$331 Roundtrip, just found
$331
Roundtrip
just found
Select Frontier Airlines flight, departing Sun, Aug 2 from Lambert-St. Louis Intl. to Denver Intl., returning Sat, Aug 8, priced at $331 just found

Airfares from $49 One Way, $100 Round Trip from St. Louis to Boulder

Prices starting at $100 for return flights and $49 for one-way flights to Boulder were the cheapest prices found within the past 7 days, for the period specified. Prices and availability are subject to change. Additional terms apply.

Mon, Aug 17 - Mon, Aug 24
STL
St. Louis
DEN
Denver
$100 Roundtrip, found 1 day ago
$100
Roundtrip
found 1 day ago
Select Frontier Airlines flight, departing Mon, Aug 17 from St. Louis to Denver, returning Mon, Aug 24, priced at $100 found 1 day ago
Sun, Sep 6 - Fri, Sep 11
STL
St. Louis
DEN
Denver
$101 Roundtrip, found 2 days ago
$101
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Sun, Sep 6 from St. Louis to Denver, returning Fri, Sep 11, priced at $101 found 2 days ago
Fri, Sep 11 - Mon, Sep 14
STL
St. Louis
DEN
Denver
$103 Roundtrip, found 7 hours ago
$103
Roundtrip
found 7 hours ago
Select Frontier Airlines flight, departing Fri, Sep 11 from St. Louis to Denver, returning Mon, Sep 14, priced at $103 found 7 hours ago
Fri, Sep 11 - Thu, Sep 17
STL
St. Louis
DEN
Denver
$109 Roundtrip, found 3 days ago
$109
Roundtrip
found 3 days ago
Select Frontier Airlines flight, departing Fri, Sep 11 from St. Louis to Denver, returning Thu, Sep 17, priced at $109 found 3 days ago
Thu, Aug 20 - Mon, Aug 24
STL
St. Louis
DEN
Denver
$113 Roundtrip, just found
$113
Roundtrip
just found
Select Frontier Airlines flight, departing Thu, Aug 20 from St. Louis to Denver, returning Mon, Aug 24, priced at $113 just found

Boulder economy flight packages

Price found within the past 48 hours. Click for updated prices.
Hotel Teatro
4.5-star property

Hotel Teatro

9/10 Wonderful! (1,360 reviews)

Aug 27 - Aug 30

3 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Price was $520, price is now $410 per person
$410
per person
found 1 day ago
Great location and staff

Reviewed on Jul 23, 2026

Patterson Inn
3.5-star property

Patterson Inn

9.6/10 Exceptional! (804 reviews)

Aug 27 - Aug 30

3 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $702, price is now $509 per person
$509
per person
found 1 day ago
Great place! Great breakfast!

Reviewed on Jul 23, 2026

Tivoli Lodge
4.0-star property

Tivoli Lodge

9.2/10 Wonderful! (1,148 reviews)

Sep 3 - Sep 8

5 night stay

St. Louis (STL) to Denver (DEN)

United • Roundtrip • Coach
Price was $932, price is now $736 per person
$736
per person
found 1 day ago
I stayed at Tivoli Lodge for two nights on vacation. The hotel’s biggest strength is its excellent location, making it easy to walk to nearby attractions and enjoy the area. My room was clean and comfortable, and overall the property was well maintained. Unfortunately, a few issues took away from the experience. The room had a persistent slightly musty, sewage-like smell that never completely went away. In addition, the front desk staff were consistently unfriendly and didn’t make me feel welcome. While they weren’t rude, their overall attitude left a poor impression throughout my stay. One other downside was the parking fee, which was $45 per day and felt expensive. Overall, Tivoli Lodge has a great location and comfortable accommodations, but the unpleasant odor in the room, unwelcoming customer service, and high parking cost made the experience less enjoyable than I had hoped.

Reviewed on Jul 24, 2026

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More About Flying To Boulder from St. Louis

Route Information for Flights from St. Louis to Boulder

Origin Airport IATA Code
STL
Destination Airport IATA Code
DEN
Distance
Direct Flight Airlines
Earliest Flight Arrival
Latest Flight Arrival

St. Louis to Boulder

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Frequently asked questions

Are there non-stop flights from St. Louis to Boulder?
There certainly are. In fact, there are 3 airlines that will fly you directly from Lambert-St. Louis Intl. Airport (STL) to DIA airport. Book your ticket with one of these popular carriers:

  • Southwest Airlines
  • United Airlines
  • Frontier Airlines

What is the shortest flight from St. Louis to Boulder?
It can take as little as 2 hours and 15 minutes to jet from Lambert-St. Louis Intl. Airport (STL) to DEN. Relax and enjoy those window views, because you'll be landing in a heartbeat.
What airlines fly from St. Louis to Boulder most frequently?
Take a look at Southwest Airlines (WN). This airline offers some of the most frequent flights from STL to Denver, CO (DEN-Denver Intl.). It operates 160 services on this route each month and is a favorite among travelers. Also explore the rewarding deals from United Airlines (UA). Offering 121 flights each month between St. Louis and Boulder, they'll ensure your journey is just as enjoyable as the destination.
What is the cheapest day of the week to fly?
Consider flying out early in the week to save on your airfare. Orbitz data from 2021 shows that Monday is the cheapest day to depart, followed by Tuesday. Saturday showed the highest average ticket prices likely because many travelers prefer to start their vacation on a weekend.
What is the cheapest month to fly?
We won't keep you guessing, according to Orbitz data from 2021, the cheapest month to fly is February. Perfect for those who need a weekend getaway, or just a break from it all in the shortest month of the year. Be aware that the most expensive time to fly is during the height of summer in July, and in the holiday month of December.*According to flight demand on Orbitz.com from January to December 2021. Savings are subject to change based on departure location, date and destination.

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Fare, taxes & fees: Fares include all taxes and fees, except baggage fees. Rates shown reflect fares found by other Orbitz users over the past 7 days. Due to rapidly changing airline prices & seat availability, these fares may no longer be available.

Refunds/changes/cancellations: Itinerary changes, if permitted for the fare, will have a $30 service fee charged by Orbitz. Additional airline charges may apply.

Other conditions: Schedules, fares and rules are subject to change without notice. Seats are limited and may not be available on all flights/dates or in all markets. Lower fares may be available. Fares will not be honored retroactively or in exchange for any wholly/partially unused ticket. Tickets are non-transferable and non-refundable. Fare rules are provided for the selected itinerary before booking.