The degree that an individual insect species is responsible for pollinating P. harringtonii varies between occurrence locations and years.

The plant's nearest relatives are other species within the section Courulei, such as P. arenicola, P. cyathophorus, and P. secundiflorus.

[11] Penland named the species Penstemon harringtonii for Harrington, a noted Colorado botanist.

[12][1] Penstemon harringtonii is a species narrowly endemic to northwestern and north-central Colorado in the United States.

[8][2]: 3  Its range spans a 132 by 77 kilometers (82 by 48 mi) area on both sides of the Colorado River drainage in the Rocky Mountains.

[2]: 3, 17 [3] The species prefers sandy soil in the arid sagebrush steppe between elevations of 2,000 and 2,900 meters (6,400 and 9,400 ft).

[13][2]: 10  As of 2006[update], the entire population of an estimated 40,000 to 43,000 individuals was spread across 40 square kilometers (10,000 acres) of occupied habitat.

William Alfred Weber and Ronald Wittmann made the sole collection of P. harringtonii at its only known occurrence in Summit County in 1982.

[2]: 10, 15 As of 2006[update], a United States Forest Service-sponsored conservation assessment on the species reported there were 74 known occurrences of P. harringtonii.

[2]: 18 The plant's NatureServe conservation status is G3, meaning Penstemon harringtonii is considered "vulnerable".

[8] As of 2020[update], P. harringtonii was a Bureau of Land Management special status species, listed as "sensitive".