An Angler's guide to the most effective patterns for fly fishing Colorado's high country

When it comes to fly fishing in Rocky Mountain National Park, success often comes down to the flies you carry. With over 150 miles of fishable streams and dozens of alpine lakes, RMNP offers an incredible variety of waters—and an equally diverse selection of hatches and food sources for trout.

At St. Peter’s Fly Shop, we’ve spent countless days dialing in what works best on these waters. Whether you're casting dry flies in Moraine Park, tossing terrestrials on Glacier Creek, or nymphing deep pools in the Big Thompson, the right fly makes all the difference.

Here are some of our top fly patterns for Rocky Mountain National Park—flies we never leave behind and always recommend to anglers heading into the park.

1. Fathead Beetle

When summer hits and the meadows warm up, terrestrials like beetles become essential. The Fathead Beetle floats like a cork and has a bold, visible profile that trout find irresistible. It’s especially deadly in slower runs and grassy cutbanks where beetles naturally fall into the water. Try this pattern in Moraine Park or upper Fall River during late July through September. Don't forget to try it out on the Park's abundant lakes as well. Beetle patterns can be the key to success on windy days in the high country.

2. Rocky Mountain Mint

This local favorite blends high visibility with low-profile finesse. The Rocky Mountain Mint is a hybrid attractor that imitates a wide variety of insects, most notably the mayfly. This pattern makes it perfect for prospecting water when no hatch is obvious, but the silhouette of a mayfly is hard for most trout to resist. It’s a go-to for cutthroat in alpine lakes and upper stream reaches, especially under bright skies.

3. Chubby Chernobyl

A high-floating attractor and hopper/large beetle imitation, the Chubby Chernobyl is hard to beat during late summer. Its buoyancy makes it an ideal top fly in dry-dropper rigs, supporting heavy nymphs in fast water, or long dropper rigs to a chironomid or midge pattern in alpine lakes. It’s a must-have for Glacier Creek pocket water and riffles throughout the park. Plus, it draws explosive eats during terrestrial season.

4. Parachute Adams

No fly box is complete without the Parachute Adams. This versatile dry fly imitates a range of mayflies and midges and works almost year-round. It excels during summer mayfly hatches on Fall River, the Big Thompson, and even high-elevation lakes. We often fish it solo or as the top fly in a lightweight dry-dropper setup.

5. Griffith’s Gnat

When trout are sipping on tiny midges or emerging bugs, especially on calm alpine lakes, the Griffith’s Gnat can save your day. This simple but effective pattern fools picky fish in glassy water. Try it in the early morning or evening when fish are rising subtly and you’re tempted to say “nothing’s working.”

6. Hippie Stomper

Equal parts fun and effective, the Hippie Stomper is a flashy terrestrial and attractor that works great in the faster water of Glacier Creek and the Big Thompson. It’s also a top pick for beginner anglers thanks to its visibility and durability. It floats high, triggers strikes, and doubles as a great indicator on dry-dropper rigs.

7. Prince Nymph

One of the most reliable subsurface patterns around, the Prince Nymph imitates a variety of aquatic insects, including stoneflies and mayfly nymphs. It’s deadly in deeper pools and pocket water. Fish it under a hopper or chubby, or swing it through tailouts on any of RMNP’s main rivers.

8. Poison Tung

This ultra-productive, tungsten-beaded midge nymph is a workhorse for anglers targeting fish in clear, cold water. The Poison Tung sinks quickly, cuts through fast current, and is ideal for deeper holes on the Big Thompson or Glacier Creek. Fish it as a dropper or part of a two-fly nymph rig for high-sticking runs and seams. The Poison Tung also makes for a great small chironomid/midge dropper off of a Chubby Chernobyl or beetle on RMNP's alpine lakes.

9. Guides Choice Hare’s Ear Nymph

An all-time classic with a twist that gets the job done day in and day out. The Guides Choice Hare’s Ear imitates everything from mayflies to caddis larvae, and its buggy look makes it a favorite for prospecting. Fish it under a dry in shallow runs or pair it with a heavier nymph to bounce deeper pools.

10. Elk Hair Caddis

This classic Caddis pattern is still our favorite go to for the park. Whether its the alpine lakes or small creeks, the high floating visible pattern shines bright all summer long.

Choose your favorite sizes and colors in our Rocky Mountain National Park Fly Collection HERE.

What Makes These Flies So Effective in RMNP?

Rocky Mountain National Park’s trout are wild, often selective, and feed on a wide range of natural insects—especially midges, mayflies, caddis, and terrestrials. Each of these patterns has earned its place in our guide packs through seasons of proven performance. They’re versatile, visible, and consistently produce in the varied conditions that RMNP throws our way.

Need Help Picking the Right Flies? We’ve Got You Covered.

If you’re heading into the park and want to be fully stocked, swing by St. Peter’s Fly Shop. We’ll help you dial in the right patterns for the season, the water you’re fishing, and the trout you’re after. Better yet—book a guided fly fishing trip and let our experienced guides show you where and how to fish these flies for the best results.

Whether you’re casting a beetle into a meadow stream or nymphing a Prince Nymph through a boulder-strewn run, these patterns will give you the confidence and success you need in Rocky Mountain National Park.

Let St. Peter’s Be Your Guide

One of the most informative spots for information on the park regarding flies in the park, can also be found in A Fly Fishing Guide to Rocky Mountain National Park by Author Steven Schweitzer. This book details locations, flies and everything one could need to explore this majestic park and it's waters. He will also be joining us onSaturday, June 7th(Sage Day)from 1pm - 3pm, for an exclusive book signing and presentation. Be sure to RSVP to the South Shop at 970-377-3785 or email shop@stpetes.com to reserve your spot, as space is limited.

*A deposit is required for booking.  All deposits are refundable, minus the 5% cancellation fee, up to 30 days prior to your trip.  All cancellations within 30 days of trip are subject to forfeiture of deposit. Health and medical issues do not change the cancellation policy. If you have any concern about the need to cancel, we recommend you purchase trip insurance to cover costs.*