Speed skating is a technical endurance sport. Still, little is known about technical changes in junior speed skaters. Therefore, changes in technique throughout a 1500-m time-trial of elite junior speed skaters is investigated to explore differences between sexes, performance levels and competitive seasons. At (inter)national 1500-m competitions, knee and push-off angles were obtained for 120 elite junior speed skaters (56 female, 64 male, age 17.6±1.1 years) per lap at 250m (lap 1), 650m (lap 2), 1050m (lap 3) and 1450m (lap 4). Additionally, 1500m end-times and lap-times were obtained to divide skaters in faster and slower performance groups and to analyze pacing behavior. Fifteen skaters (8 female, 7 male, age 17.3±1.5 years) were measured again after 1.6±0.6 years. (Repeated measures) ANOVAs were used for statistical analyses (p<0.05). ICC, determined in a pilot study, was 0.55 for knee and 0.76 for push-off angles. Elite junior speed skaters increased their knee angles throughout the race (p<0.005), regardless of sex (p = 0.110) or performance level (p = 0.714). Push-off angles increased from lap 1-3 (p<0.001), in which men showed a larger decay than female skaters (p<0.05), this holds for both performance groups (p = 0.103). Faster skaters had smaller knee and push-off angles than slower skaters (p<0.05). Males showed smaller body angles than females (p<0.001). Faster male and female skaters showed a relative slower start and faster lap 3 compared to slower skaters (p<0.05). Development over competitive seasons showed a shift towards smaller push-off angles (p = 0.038) and less decay in knee angles from lap 2-3 (p = 0.026). The present study shows that technique throughout the 1500m deteriorates. Deterioration in technique is regardless of performance level, even with different pacing behaviors. Differences between sexes were found for push-off angles. The longitudinal development suggests changes in technique towards senior level and highlights the importance of studying juniors separate from seniors.