[citation needed] On his return from Germany in 1899, Reisner organized his first archaeological expedition to Egypt (1899-1905), funded by philanthropist Phoebe Hearst.

In subsequent seasons, he excavated the Middle Kingdom sites of Deir el-Ballas and El-Ahaiwah, where he developed an archaeological methodology that characterized his work from that moment on.

[8] In 1907, Reisner was hired by the British occupation government in Egypt to conduct an emergency survey in northern Nubia in response to potential damage of archaeological sites during the construction of the Aswan Low Dam.

[8] After a decade in Egypt, Reisner headed the Harvard excavation of Samaria, first in 1908 together with Gottlieb Schumacher, and for a second time in 1910, when he discovered written documents testifying the presence of an Egyptian population in 8th century BCE Palestina.

His studies in the Pyramid field of el-Kurru led him to reconsider the role of this royal cemetery, where kings of the 25th dynasty of Egypt were buried.

[12] Reisner found the skull of a Nubian female (who he thought was a king) which is in the collection of the Peabody Museum of Archaeology and Ethnology at Harvard.

Arthur Merton (London Times) remarked in 1936 in the aftermath of the Abuwtiyuw discovery that Reisner "enjoys an unrivalled position not only as the outstanding figure in present-day Egyptology, but also as a man whose soundness of judgement and extensive general knowledge are widely conceded.

He insisted on the importance of recording every discovery in order to provide comprehensive interpretations of a site, taking into account the debris and minor artifacts.

Reisner advanced a theory of stratigraphy in an appendix of his manual Archaeological Fieldwork in Egypt: A Method of Historical Research, published posthumously.

[15] Reisner's views on Nubia were conditioned by the theoretical ideas of his own time, many of which were based on racist considerations about the progress and decline of cultures.