In this paper, the design and performance of partial-state controllers with incomplete multi-actuation systems for the seismic protection of tall buildings is investigated. The proposed approach considers a partially instrumented multi-story building with an incomplete system of interstory force-actuation devices implemented at selected levels of the building, and an associated set of collocated sensors that measure the interstory drifts and velocities corresponding to the instrumented stories. The main elements of the proposed controller design methodology are presented by means of a twenty-story building with two different actuation schemes. For these control configurations, partial-state controllers are designed following a static output-feedback H8 controller design approach, and the corresponding frequency and time responses are investigated. The obtained results clearly indicate that the proposed partial-state controllers are effective in mitigating the building seismic response. They also show up that a suitable distribution of the instrumented stories is a relevant factor in the control system design.