Understanding the daily energy expenditure of athletes during training is important to support recovery, adaptation, and the maintenance of performance. The aim of the current research was to assess the total daily energy expenditure (TDEE) and the acute energy expenditure (EE) of tennis training sessions during habitual training of elite tennis players. Using a cohort study design, 27 (n = 10, male; age; 22.3 ± 3.2years and n = 17, female; age: 23.8 ± 3.5years) elite singles tennis players were assessed for TDEE and tennis training EE. Using Actiheart activity monitors during a 2- to 5-day training period, male players were analyzed for 26days and 33 (1.3 ± 0.5sessions/day) tennis training sessions, and female players for 43days and 58 (1.2 ± 0.4sessions/day) tennis training sessions. Male TDEE (4,708 ± 583kcal/day) was significantly higher than female (3,639 ± 305kcal/day). Male absolute and relative tennis training EEs (10.2 ± 2.3kcal/min and 7.9 ± 1.4kcal·hr-1·kg-1) were significantly higher than those of females (7.6 ± 1.0kcal/min and 6.8 ± 0.9kcal·hr-1·kg-1). The resting metabolic rate was assessed via indirect calorimetry. The physical activity level for both groups was 2.3AU. The TDEE of male and female players during habitual training now highlights the continual cycle of high energy demands experienced by the elite tennis player. The broad ranges of TDEE and EE reported here suggest individual assessment and nutritional planning be prioritized, with a particular focus on carbohydrate requirements.