Pacing is the goal-directed distribution of effort across an event to cover a set-distance in the shortest time. Athletes’ pre-race expectations may influence performance and this study investigated the effect of positive and negative expectations on running time-trial pacing. Male athletes (n = 11) 200 m split times were recorded over seven 1000 m self-paced time-trials (three baseline, four experimental). The experiment consisted of four conditions: informed caffeine/given caffeine (CC 3.5 mg/kg); informed caffeine/given placebo (CP); informed placebo/given caffeine (PC); informed placebo/given placebo (PP). Conditions CC and CP were positive expectations of receiving caffeine to improve performance and PC and PP were negative expectations of receiving a placebo to not affect performance. Average 1000 m speeds were: CC = 5.80 ± 0.26 m/s; CP = 5.81 ± 0.27 m/s; PC = 5.75 ± 0.26 m/s; PP = 5.67 ± 0.29 m/s; Baseline = 5.70 ± 0.24 m/s, with CC and CP faster than each other trial (Effect size (ES)=0.2–0.3). Initial 0–200 m speed was greater on CC (0.1–0.2 m/s faster; ES =  0.2–0.3) and CP (0.2 m/s faster; ES = 0.3–0.4) compared to PC and PP, respectively. A non-trivial increase in speed from 800–1000 m was solely observed on CC (5.78 ± 0.35 m/s), relative to speeds between 600–800 m on CC (5.69 ± 0.33 m/s; ES = 0.3), Baseline speed from 800–1000 m (5.59 ± 0.36 m/s; ES = 0.4) and speeds on each other trial from 800–1000 m (5.62–5.70 m/s; ES=0.2–0.3). A clear expectancy effect from caffeine ingestion was observed on pacing over the initial 200 m of a 1000 m time trial, both positive (CC and CP) and negative (PC and PP). In contrast, an ‘end-spurt’ was only observed when both positive expectancy and potential physiological effects were present (CC trial), despite similar overall performance on CC and CP. These results indicate that caffeine ingestion and expectancy can influence pacing strategy in running. Developing negative pre-race expectations may harm middle-distance athletes’ performance by beginning at a sub-optimal speed.