Roughly 25 miles long, the Gardner River flows from the high alpine Gallatin Range in northwestern Yellowstone National Park (Wyoming) to its confluence with the Yellowstone River at Gardiner, Montana. This waterway is known for its rugged canyon beauty and excellent trout fishing, especially for wild cutthroat and rainbow trout. Though smaller than the Yellowstone, the Gardner is a premier fly-fishing river in the park, offering diverse habitats—from gentle meadow runs in Gardner’s Hole to turbulent pocket water tumbling through volcanic canyons—along with unique features like the Boiling River hot spring.
Anglers typically divide the Gardner into three segments. **Headwaters (Gardner’s Hole above Osprey Falls)** flow through broad subalpine meadows fed by small tributaries (Fawn, Panther, Indian, Obsidian creeks), yielding fast action for small brook trout. **Sheepeater Canyon (Osprey Falls to Boiling River)** plunges through a steep, basalt-walled gorge with limited foot access; as the canyon opens and the gradient eases approaching the Boiling River, trout grow larger and more plentiful. **Lower Gardner (Boiling River to Yellowstone confluence)** is warmed by geothermal inflow and lies at the park’s lowest elevation, resulting in richer insect hatches and season-long fishability; fall-spawning brown trout from the Yellowstone boost the trophy potential in this stretch.
The Gardner supports a true wild "grand slam" of trout species. Above Osprey Falls the cooler headwaters hold mostly brook trout (technically a char). Below the falls, the river offers a mix of rainbow trout, brown trout, Yellowstone cutthroat trout, and hybrid cuttbows, along with native mountain whitefish. Most fish are 8–14 inches in these middle and lower reaches, with some 15–20 inchers closer to the Yellowstone confluence. Each autumn, large migratory brown trout run up from the Yellowstone River to spawn in the Gardner, giving anglers a shot at trophy-size fish during the fall season. Native Yellowstone cutthroat and whitefish remain a conservation priority, with park regulations requiring their release.
High spring flows begin subsiding by late June, when the Gardner sees prolific stonefly hatches. Giant salmonflies and golden stones emerge in early summer, triggering explosive feeding in the canyon riffles. As these big bugs wane, abundant caddisfly hatches take over on summer evenings, with Pale Morning Duns and other mayflies providing steady action on sunny afternoons. By mid-July, terrestrial season is in full swing: hoppers, beetles, and ants blown in from the banks keep trout looking up through September. In autumn, aggressive pre-spawn brown trout chase sculpins and baitfish, while blue-winged olive mayflies and midges reward anglers willing to nymph the colder late-season waters. The Boiling River’s thermal influence can keep the lower Gardner productive even into winter months.
This is primarily a walk-and-wade fishery, so a versatile 8½–9 foot rod in 4 or 5 weight is ideal (with a lighter 3-weight fun for the brookie-filled headwaters). Early in the season and again in late fall, fishing a high-sticking nymph rig with rubber-legged stonefly nymphs or beadhead attractors is the most effective way to probe the deep, cold pockets. Once water temperatures climb above ~55 °F in summer, switch to big dry flies—such as foam salmonfly imitations or bushy Royal Wulffs—tight against pockets and banks, as trout will readily smash large dries in the turbulent water. A dry-dropper setup (hopper with a small beadhead dropper) is deadly in late summer when fish are feeding opportunistically on terrestrials and subsurface nymphs. In autumn, try stripping a small olive sculpin or Woolly Bugger at dawn for a chance at a pre-spawn brown, but expect most of your success to come from dead-drifting flies through runs and seams.
Despite its backcountry character, the Gardner has several well-known fishing areas. **Gardner’s Hole (headwaters)** near Indian Creek Campground offers easily accessible meadow water with eager brook trout, especially around the confluences of feeder creeks. **Sheepeater Canyon** between Osprey Falls and Mammoth is far less crowded—much of it requires a hike into steep terrain—but rewards adventurous anglers with unpressured pocket water holding rainbows, browns, and cutthroat in surprising places. In the **Lower Gardner**, the popular 45th Parallel trail near Mammoth Hot Springs leads to the Boiling River area and downstream pools, where larger trout congregate (and where fall-run browns from the Yellowstone swell the ranks). These lower reaches and tributary mouths (Fawn, Indian, Panther creeks) can be especially productive in late summer and fall.
All of the Gardner River lies within Yellowstone National Park, so access is via park roads and trails rather than formal state fishing sites. The Mammoth–Norris road crosses the upper Gardner near Indian Creek, providing entry to the headwaters and above-Falls sections. Farther north, anglers traditionally reached the lower river from pullouts along the Mammoth–Gardiner road, but the historic 2022 flood destroyed portions of that road that paralleled the river. As a result, sections near the Boiling River and downstream now require hiking in (for example, along the old roadbed trail from the 45th Parallel parking area). Some backcountry canyon areas remain closed or challenging to reach—check with park rangers for current trail conditions and closures before planning a trip. In general, be prepared for rugged walks and no facilities; there are no boat launches since the Gardner is not floatable.
A selection of high-floating dry flies and sturdy nymphs is essential for the Gardner’s fast water. In June and July, large stonefly patterns (foam Salmonfly and Golden Stone imitations, size 6–10) or attractor dries like PMX, Stimulators, and Royal Wulffs (#12–14) turn trout heads. Through late summer, a hopper-dropper rig is a go-to: e.g. a foam hopper or tan chubby Chernobyl with a beadhead stonefly or Prince nymph dropper works well during the prolific Yellow Sally and terrestrial season. Carry a range of smaller caddis and mayfly imitations (Elk Hair Caddis, Adams, etc. in #14–18) for evening hatches, and a few streamer patterns (size 6–8 Woolly Buggers or sculpins) to entice bigger browns in the fall. A shorter 7.5–9 ft leader helps in pocket water (use 3X–4X tippet for big dries and 4X–5X for smaller flies). Because felt-soled boots are banned in Yellowstone to prevent aquatic invasives, wear rubber-soled wading boots (studs recommended for the slick, rock-strewn river) and consider using a wading staff for stability. Polarized sunglasses are also invaluable for spotting fish and navigating glare on the water.
The Gardner’s ecosystem faces both natural and human-caused challenges. A historic, unprecedented flood in June 2022 dramatically altered stream channels and banks along the Gardner River, underscoring the river’s susceptibility to extreme runoff events. Native fish conservation is a top priority in Yellowstone: cutthroat trout and mountain whitefish are protected, while anglers are encouraged to harvest invasive brown and rainbow trout to reduce competition and hybridization. Preventing the spread of aquatic invasive species (AIS) is critical—park regulations mandate cleaning and drying all gear and prohibit felt-soled wading boots. During summer heat or drought, the park may temporarily close the Gardner to fishing when water temperatures become too warm for trout survival. Anglers can help by respecting these closures, participating in volunteer programs (like Trout Unlimited-supported habitat restorations and fish surveys), and practicing Leave No Trace ethics along this pristine river.
The Gardner River demands caution and preparedness from anglers. Much of the river runs through rugged canyons with slippery boulders and fast, cascading currents—good balance and careful wading (preferably with a wading staff) are essential to avoid falls or injuries. There are no maintained exits in the steepest stretches, so if you venture into Sheepeater Canyon be aware that rescue or cell service is unlikely. Sudden rainstorms can rapidly muddy the river and spike flows due to the watershed’s steep gradient; always watch upstream for rising water and check forecasts, especially during summer thunderstorms. Wildlife is another concern in this remote area: the Gardner corridor is prime habitat for elk, bison, and even grizzly bears. Carry bear spray and travel in groups whenever possible, remain alert for bear sign (tracks or scat), and never fish near carcasses or approach wildlife. Finally, obey any trail closures or hazardous area signs left in the wake of the 2022 flood, and consult park rangers if unsure about current conditions.
**Parks’ Fly Shop** (Gardiner) is a historic, full-service outfitter located at the park’s north entrance, with roots dating back to the 1950s and decades of expertise on the Gardner and surrounding Yellowstone waters. **Sweetwater Fly Shop** (Livingston) provides gear, guiding, and up-to-date advice for Yellowstone area fisheries, often helping visiting anglers prepare for park streams like the Gardner. **Montana Angler** (Bozeman) offers guided trips on the Gardner River in addition to other regional waters, sharing detailed fishing reports and hatch information for Yellowstone National Park destinations. All of these shops are welcoming to newcomers and can supply the proper flies, current conditions, and even arrange instruction or shuttles for anglers exploring the Gardner.
Anglers can support the Gardner River’s fishery through involvement with regional conservation groups. **Montana Trout Unlimited** (Montana TU) coordinates volunteer chapters across the state that work on habitat restoration and native fish projects, including efforts benefiting Yellowstone Park waters. The **Greater Yellowstone Coalition** engages in scientific research and advocacy to keep the Greater Yellowstone Ecosystem’s rivers wild and free from threats (such as pollution or proposed mining near park boundaries). At the national level, **Trout Unlimited’s Yellowstone Basin Initiative** provides funding and expertise for native trout restoration and even post-flood recovery work in Yellowstone streams. These organizations welcome donations and volunteers—joining a stream cleanup day or citizen science project is a great way to give back to the Gardner’s pristine environment.
Because the Gardner River lies entirely inside Yellowstone National Park, anglers must have a Yellowstone Park fishing permit (state licenses are not valid and not required) and follow park-specific rules. Starting in 2025, the Gardner from Osprey Falls downstream to the Yellowstone confluence is open to fishing year-round, making it one of the only park waters with winter access. Standard park regulations apply: fishing is fly or lure only (no bait) with barbless hooks required, and all native fish species—Yellowstone cutthroat trout and mountain whitefish—are catch-and-release only. Non-native trout (brown, rainbow, brook) may be harvested and possession limits are liberal or unlimited to encourage removal of these species. Additional Yellowstone rules include a ban on felt-soled wading footwear to prevent aquatic invasive species, a sunrise-to-sunset fishing day, and seasonal area closures for bear management or warm water conditions. Always consult the park’s current fishing regulations summary before fishing, as rules and closures can change annually.