Postnatal growth and vocalization development in the lesser horseshoe bat, Rhinolophus cornutus, were investigated in the Kyushu District. Parturition occurred in early June. Forearm length of newborn young averaged 16.5 mm in females and 16.3 mm in males, and their body weight averaged 2.4 g. The newborn young at a few days of age were left alone or in a small loose cluster at night. However, mothers returned to the nursery roost from foraging one or two hrs after sunset and embraced their young until sunset, while mothers embraced them three hrs after sunset at colony-forming stage. From newborn to colony-forming stage, forearm length and body weight of young increased noticeably, whereas from colony forming to flying stage growth rates slightly slowed down, especially the rates being more marked in a large colony than in a small colony. From flapping to flying stage, there were two peaks of mother's embracing behavior at night, while most of the young clustered tightly and formed a large colony. Fundamental frequency of calls in a few-day-old young averaged 19.8 kHz. From newborn to colony-forming stage, the number of harmonics reduced 5–6 to 3–4 in both the oral and nasal calls. At flapping stage, oral calls with two or three syllables, contained two or three harmonics, and their fundamental frequency averaged 32.1 kHz, while nasal calls contained only two harmonics, and their frequency averaged 42.6 kHz. At flying stage, young emitted nasal pure tone CF-FM or FM-CF-FM calls, and the second harmonic became more intense than the first one. The dominant frequency of CF-components from flying to self-supporting stage is negatively correlated with the size of forearm length.