The first investigation of the known triple system 55 UMa (2.55d binary in a ~1870-d orbit with the third star) based on electronic spectra led to several new findings about the system: (1) Discovery of spectral lines of the tertiary and an unambiguous detection of the lines of the secondary. Spectra of both primary and tertiary are of the same strength and correspond to spectral class A0V. The secondary spectrum is about twice fainter in the visual region and belongs probably also to spectral class A. (2) First self-consistent orbital solution describing close and wide orbit and the detection of apsidal motion for the close pair. The orbital period of the close pair was improved to (2.5538380+/-0.0000046d) and basic physical elements for all three stars and the system were estimated. The orbital solution also gives the period of apsidal motion of the close pair of (450+/-60)yr and leads to a good agreement with the published speckle-interferometric orbit for the distant companion if the longitude of periastron passage is increased by 180deg.