Best Fly Fishing Spots in Boulder County, Colorado

Boulder County, Colorado, is a fly fishing paradise with its pristine mountain streams, crystal-clear lakes, and abundant trout populations. Whether you're a seasoned angler or a beginner looking to cast your first fly, Boulder County offers some of the best fly fishing opportunities in the Rocky Mountains. In this guide, we’ll explore the top fly fishing spots in Boulder County, the best times to fish, and essential tips to help you make the most of your fishing adventure.

Boulder Creek – A Local Favorite

Location: Runs through Boulder and into the foothills
Fish Species: Brown trout, rainbow trout, brook trout
Best Techniques: Dry flies, nymphing, small streamers

Why Fish Here?
Boulder Creek is one of the most accessible and productive fly fishing destinations in Boulder County. It runs right through the city, offering urban fishing opportunities, but the best fishing is found in the upper sections west of Boulder, where the creek flows through scenic mountain canyons.

Highlights:

• Easy access from downtown Boulder

• Great for beginners and experienced anglers

• Consistent hatches provide excellent dry fly action

Pro Tip: Head to Boulder Canyon (west of town) for less pressured water and bigger trout.

South Boulder Creek – Stunning Mountain Scenery

Location: Flows from Gross Reservoir down to Eldorado Canyon
Fish Species: Wild brown trout, rainbow trout, cutthroat trout
Best Techniques: Dry-dropper setups, Euro nymphing, small dry flies

Why Fish Here?
South Boulder Creek is a hidden gem for fly fishing in Boulder County. The tailwater section below Gross Reservoir is one of the best places to catch wild brown trout, with consistent flows and excellent insect hatches.

Highlights:

• Clear, cold water year-round

• Abundant wild trout population

• Scenic canyon views and wildlife sightings

Pro Tip: Use small dry flies (size 18–22) and light tippet (5X–6X) for the best success in the technical tailwater section.

St. Vrain Creek – A Diverse Fishery

Location: Near Lyons, CO, flowing into Longmont
Fish Species: Brown trout, rainbow trout, cutthroat trout
Best Techniques: Nymphing, dry flies, soft hackles

Why Fish Here?
St. Vrain Creek offers a mix of freestone and tailwater fishing, making it an exciting and diverse fishery. The North and South Forks near Lyons provide excellent small-stream fishing, while the main stem through Longmont offers easy access for urban anglers.

Highlights:

• Multiple sections with different fishing styles

• Beautiful, clear water with plenty of trout

• Less crowded than Boulder Creek

Pro Tip: Try the North Fork near Button Rock Preserve for bigger fish and fewer anglers.

Left Hand Creek – A Hidden Gem

Location: North of Boulder, near Jamestown
Fish Species: Brown trout, rainbow trout, brook trout
Best Techniques: Dry flies, Euro nymphing, small streamers

Why Fish Here?
Left Hand Creek is a lesser-known fly fishing spot, perfect for anglers looking to escape the crowds. The creek is small and technical, but the rewards are plentiful, with feisty wild trout in a peaceful mountain setting.

Highlights:

• Great for solitude and backcountry fishing

• Small, wild trout that aggressively take dry flies

• Easy wading and picturesque surroundings

Pro Tip: Go early in the morning or late in the evening for the best dry fly action.

Gross Reservoir – High-Elevation Fishing

Location: Southwest of Boulder
Fish Species: Lake trout, brown trout, rainbow trout
Best Techniques: Streamers, nymph rigs, deep water tactics

Why Fish Here?
Gross Reservoir is one of the best places in Boulder County for targeting large trout. The deep, clear waters hold big lake trout, and the inlet streams provide great fishing for brown and rainbow trout.

Highlights:

• Great for both fly fishing and spin fishing

• Stunning alpine scenery

• Opportunity to catch trophy-sized fish

Pro Tip: Use sinking lines and big streamers for a chance at a trophy lake trout in deeper water.

Brainard Lake & Indian Peaks Wilderness – Backcountry Adventure

Location: Near Ward, CO
Fish Species: Cutthroat trout, brook trout
Best Techniques: Dry flies, small nymphs, tenkara fishing

Why Fish Here?
For anglers who love hiking and fishing in pristine alpine settings, Brainard Lake and the surrounding high-country streams are unbeatable. These waters hold wild cutthroat and brook trout that eagerly take dry flies.

Highlights:

• Gorgeous mountain lakes and streams

• Easy wading and sight fishing

• Less fishing pressure than lower-elevation rivers

Pro Tip: Hike up to Lake Isabelle or Long Lake for spectacular scenery and aggressive cutthroat trout.

Best Seasons for Fly Fishing in Boulder County

• Spring (March – May): Best for nymphing as trout become more active. Expect runoff in late May.

• Summer (June – August): Prime dry fly season with consistent hatches. Ideal for high-elevation lakes and streams.

• Fall (September – November): Big trout move to spawn—great time for streamers and larger nymphs.

• Winter (December – February): Tailwaters like South Boulder Creek fish well year-round, but expect cold conditions.

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Ready to gear up and cast out? Whether you're looking for mountain solitude or an easy afternoon by the creek, Boulder County delivers world-class fly fishing experiences in every season. Tight lines!