This article traces the origins of Hong Kong Sign Language (hereafter HKSL) and its subsequent development in relation to the establishment of Deaf education in Hong Kong after World War II. We begin with a detailed description of the history of Deaf education with a particular focus on the role of sign language in such development. We then compare the use of sign language among Deaf students in the first two Deaf schools in Hong Kong in the postwar period, and how both signing varieties contributed to the later development of HKSL. We maintain that the modern form of HKSL is a mixture of the Nanjing/Shanghai variety of Chinese Sign Language and the signing varieties developed locally among Deaf people in Hong Kong. This finding supports Woodward's (1993) hypothesis that some form of signing must have existed in Hong Kong before Nanjing/Shanghai signs were introduced in 1948 and 1949 by a Deaf signing couple who set up the first signing school.