This study is a survey of the floristic composition of the Parker Creek watershed located in the Sierra Ancha Mountains of Arizona. This watershed includes ecological communities ranging from the Sonoran Upland Province to Rocky Mountain Montane Conifer Woodlands. The collections were conducted along designated routes within the lower and mid-upper reaches of the creek, including the inner canyon. A checklist was completed using both our new collections and several herbarium queries with the Southwestern Environmental Information Network (SEINet). This study reports the presence of 625 species, representing 335 genera and 94 families of vascular plants. The flora is predominantly comprised of angiosperms (ASU, Flowering plants), but also includes gymnosperms (conifers), lycophytes (club mosses), sphenophytes (horsetails) and pteridophytes (ASU, Ferns). A comparison to the nearby Sierra Ancha Wilderness, also located in the Sierra Ancha Mountains, revealed only 47% similarity to the Parker Creek watershed species.