Animal movement is often largely determined by abiotic conditions of the surrounding environment. While a large body of work has improved our understanding of how different substrate properties can impact locomotor performance, mechanics, and behavior, fewer studies have considered substrate transitions, or changes in substrate level, incline, texture, and/or compliance during a single locomotor event. Such transitions are common for animals in nature and can be particularly abrupt for high-speed animals. We investigated the occurrence and impacts of substrate compliance transitions in Rhoptropus afer, a cursorial day gecko known for its ability to sprint rapidly for several meters at a time. In addition to collecting video recordings of substrate use during escapes in the field, we conducted locomotor trials on a level trackway featuring a transition from a solid surface into and out of sand. We found that R. afer uses substrates of different compliance and transitions to and from more compliant surfaces fairly equally in the wild. Moreover, laboratory trials revealed that this species is able to maintain forward velocity during sand transitions but exhibits increased body angle and duty factor upon entering sand; this may represent active and/or passive kinematic responses to acute changes in compliance. This study provides important insight as to how geckos and other animals accommodate natural, often heterogeneous, substrate conditions during critical high-speed locomotor events, such as predator evasion.