Extended periods of resistance training (RT) induce muscle hypertrophy. Nevertheless, to date, no study has investigated the time window necessary to observe significant changes in muscle cross-sectional area (CSA) in older adults. Therefore, the present study investigated the time-course of muscle hypertrophy following 10 weeks (20 sessions) of RT in elderly. Fourteen healthy older subjects were randomly allocated in either the RT (n: 6) or control group (n: 8). The RT was composed by 4 sets x 10 repetitions (70-80% one repetition maximum [1-RM]) in a leg-press machine. The time-course of vastus lateralis muscle hypertrophy (CSA) was assessed on a weekly basis using a Mode-B ultrasonography (US). Leg-press muscle strength was assessed by dynamic one repetition maximum (1-RM) test. Our results demonstrated that RT group increased leg-press 1-RM by 42% (P < 0.05) after 10 weeks of training. Significant increases in vastus lateralis muscle CSA were observed only after 18 sessions of training (9 weeks; P< 0.05; 7.1%). In conclusion, our training protocol promoted muscle mass accrual in older subjects and this was only observable after 18 sessions of RT (9 weeks).