On 25 March 919, at the head of his fleet, Lekapenos seized the Boukoleon Palace and the reins of government. Initially, he was named magistros and megas hetaireiarches, but he moved swiftly to consolidate his position: in April 919 his daughter Helena was married to Constantine VII, and Lekapenos assumed the new title basileopator; on 24 September, he was named Caesar; and on 17 December 919, Romanos Lekapenos was crowned senior emperor.

In subsequent years Romanos crowned his own sons co-emperors, Christopher in 921, Stephen and Constantine in 924, although, for the time being, Constantine VII was regarded as first in rank after Romanos himself. It is notable that, as he left Constantine VII untouched, he was called 'the gentle usurper'. Romanos strengthened his position by marrying his daughters to members of the powerful aristocratic families of Argyros and Mouseles, by recalling the deposed patriarch Nicholas Mystikos, and by putting an end to the conflict with the Papacy over the four marriages of Emperor Leo VI.