Aim: To retrospectively describe the annual training characteristics of elite biathletes across different age groups over 2 decades. Methods: Self-documented training-diary data from 18 elite biathletes (tier 4/5, 7 ♀, 11 ♂) between 1994 and 2014 were included in the study and classified by age group (junior: 16–18 y, U23: 19–23 y, senior: >23 y). Linear mixed models were used to analyze the effect of age group on training characteristics (intensity, distance, time, and modality shooting training) for each sex. Results: Male biathletes increased their total training volume (TV) by 34% across age groups, while female biathletes did not show increasing TV with age. Endurance TV increased from junior to senior level by 35% and 23% in both men and women. The proportional distribution of low-intensity training, moderate-intensity training,, and high-intensity training was significantly different for both sexes between age groups. Senior male biathletes shot 4% and 15% more annual shots than Under-23s and juniors due to greater number of technical and in-competition shots, while females only increased in-competition shots at senior level. Conclusion: This study provides further insights into the biathlon training puzzle, suggesting sex-specific differences in training strategies from junior to senior level. Our data may emphasize the importance of increasing endurance TV from junior to senior level by increasing the proportion of low-intensity training, with a reduction in moderate-intensity training and maintenance of high-intensity training when transitioning between age groups. Increasing the number of technical shots, as well as in-competition shots, while maintaining precision-shooting volumes may also be important for biathletes’ long-term development.