Some of the better fishing smaller streams in Rocky Mountain National Park that can be found on both sides of the park are listed below.  Some may require short hikes to access. 
EAST SIDE

• Headwaters of the Big Thompson River (near Fern Lake TH)
• Roaring River (up Lawn Lake TH)
• West Creek
• North St. Vrain (Wild Basin area)
• Poudre River Headwaters
• Glacier Creek

WEST SIDE

• Colorado River Headwaters
• Onahu Creek
• Tonahutu Creek
• North Inlet Creek
• ​East Inlet Creek

Small stream fishing in Rocky Mountain National Park can be a wonderful experience.  Some short hikes will take you back into some great locations to catch trout all day long.  Look at the list above and plan your trip - and remember timing on these creeks is crucial.  Fishing small streams too early in the season can be disastrous, as many fish don't start aggressively feeding until water levels come down.  Fishing late June through August is prime fishing in the National Park.