Fly Fishing with the San Juan Worm

Complete Guide to Fly Fishing with the San Juan Worm

The San Juan Worm is no stranger to the fly-fishing world. This pattern has been around for over 50 years and, in the right conditions and waters, is unmatched in its success rate of catching fish. The pattern is a straightforward one to tie and can be fished in various ways.

The worm pattern was the impetus of the San Juan shuffle, which is now a frowned-upon activity, but it still managed to produce the much-needed worm imitation. More on the shuffle later.

Fly Fishing on the San Juan River
Fly Fishing on the San Juan River

The San Juan worm covers all worm types and has even been thought to cover the tree worm after the first rain in certain areas of New Mexico. The rain tends to knock the worms out of the trees, and they become a stand-out meal for the trout. The color of the worms is what gets them noticed because they tend to pop in the stained water from the runoff and rain.

The San Juan worm is a niche in most fly boxes and so it should be! I love to fish the worm, especially a slightly weighted version as a point fly which has proven itself time and time again.

Why the San Juan Worm is Great

When looking at the pattern, it is evident that there isn’t much to the profile or design, but in my mind, it makes such an effective pattern. The simplistic approach is critical. The small head and tail made from the burnt edges work perfectly, and the micro chenille gives the fly sufficient movement.

As fly tiers and anglers, this is what we struggle with the most: movement. Getting that natural movement of the pattern is key, and once we get something close to the natural specimen, results can be seen.

This lightweight pattern is very effective in a dead drift or on a hover line over a weed bed but adds some weight to it, and you change the whole dynamic of its profile, sink rate, and how it presents. This is what I love about fly fishing and this pattern, and its versatility is just incredible.

A Little History of the San Juan Worm

So, originally designed and tied in the 70s, Jim Aubrey needed a pattern to imitate the insects kicked up by the San Juan shuffle. Now seen as an unsportsmanlike like activity and barred in most places, Jim Aubrey knew he needed a simple worm pattern to cover most of the aquatic life kicked up.

Enter the San Juan worm. Simple, effective, and deadly!

What is great about this pattern is that if fished as a worm it works very well and so it should, but what makes it even more attractive is its imitation of the blood midge, which can be found in the eastside lakes and the midge larvae in the Sierran river. With a few slight changes to the weight and size you have a very versatile pattern.

What Fish Does a San Juan Worm Catch?

Originally designed to target trout but knowing what it imitates or instead can suggest, it is obviously a very attractive pattern for many other fish species. Chub, Grayling, and Carp, to name a few.

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How to Setup a San Juan Worm

With this pattern’s versatility, you will need to set up and fish it in a few various ways. Nothing too complicated but just a few changes that will help catch more fish.

The driver- setup is the same as you would fish any nymph, really. A euro nymph rig or a dry dropper-style New Zealand rig are both excellent ways to fish. Czech style wouldn’t work very well as you need to have a heavily beaded fly for this, and the San Juan worm is generally un-beaded or very lightly weighted with a 2mm or 2.5mm bead at the most. Leader 12-17 feet down to a 4X-7X tippet will work fine.

Stillwaters- Again, nothing needs to change reality for the still water setup; the worm is fished as a single terrestrial just below the surface on a midge rig. Long leaders and floating/ hover lines will be just fine.

A slow figure of eight retrieve is the best for the still waters.

GUIDE PRO TIP- Changing the bead color to a copper or hot spot can really change the triggers and success rate.

What Does the San Juan Worm Represent

With the easiest and most basic of imitations intending to be the basic bloodworm which can be found on the bottom of a riverbed, the San Juan worm pattern has a few other suggestive qualities as well.

The San Juan worm can also imitate a blood midge or various midge larvae in different stages as well. This is what makes this pattern so effective and thus a popular pattern to have for any circumstance.

San Juan Worm Favorite Size and Color

I like to have a few versions of this pattern to use in certain conditions

Beaded San Juan Worm
Beaded San Juan Worm Fly
San Juan Worm Fly Pattern
San Juan Worm Fly Pattern
San Juan Worm Flash
San Juan Worm Flash
  1. Beaded San Juan Worm– this is the perfect weighted version of this pattern. I also like the bead more forward in the pattern. This just gets the hook point riding higher in the water. Fish the pattern in pinks, purples, and reds in sizes #14- #16.
  2. San Juan Worm– this is the classic, and not much needs to be said about this pattern. Fished in sizes #14 to #16. I use heavier hooks for all my worm patterns. I don’t like my hook’s bending open.
  3. San Juan Worm Flash–  As you know, in any form of fishing, often the slightest of changes triggers an eat. This pattern variant has a little extra flash through it, which is those darker stained waters pop out a little more. The same size to be fished as the other size, #14 to #16’s

Where to Buy San Juan Worm

All worm or midge patterns are super simple to tie, and if you do tie your own flies, they should be a breeze for you. Keep the hook gape clear and use those heavier hooks for the bigger eats.

Suppose you don’t tie your own flies, no worries. I would recommend you order some from Umpqua. Or better yet, go off and support your local fly shop if you have one in your area. The San Juan pattern will definitely be part of their stock, and if it isn’t, it is fast enough to tie a few up for you with no problems.

How to Tie San Juan Worm


Hook: Size 12 Wet Nymph Hook

Thread: 6/0 Red
Body: Small Chenille San Juan Red


  1. Secure hook in the vice
  2. Start by wrapping a good thread base. If you choose to add a bead to the pattern, it is at his point you can slip it on and secure it with a few wraps.
  3. Cut off your chenille. The length is up to you. Remember that you can always cut more off. Burn the edges and roll to create that black head point.
  4. Starting from the back of the hook, secure the chenille with three tight wraps. Moving forward lightly, wrap forward towards the hook eye.
  5. Whip finish off and apply head cement.
  6. If you are tying with a bead, then secure the chenille on either side of the bead with a few tight wraps.

One Last Cast with the San Juan Worm

So, there you have it. The San Juan Worm may not be the most attractive pattern or the trickiest to tie, but it sure does catch fish. In reds, browns, and greens, they all work so well! If you don’t have space in your fly box, make some or buy another box. You can’t hit the next mission without them.

Tight Lines, All!

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Kyle Knight writer Guide Recommended

Kyle Knight

Fly fishing has been my passion and pursuit for the past 20 years. I am a South African based fly fisherman who loves nothing more than spending a day on the water. Fly fishing is more than catching fish, being in the outdoors with good friends and family is what it is all about.

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