  NA61/SHINE is a fixed target experiment at the CERN Super-Proton-
Synchrotron. The main goals of the experiment are to discover the critical
point of strongly interacting matter and to study the properties of the onset
of deconfinement. In order to reach these goals, a study of hadron production
properties is performed in nucleus-nucleus, proton-proton and proton-nucleus
interactions as a function of collision energy and size of the colliding
nuclei. In this paper, I will review recent results on strangeness production
in p+p, Be+Be and Ar+Sc collisions in the SPS energy range. Kinematic spectra
and mean multiplicities of kaons obtained with various analysis methods will be
shown. An overview of strangeness production and its dependence on system size
in the vicinity of the phase transition will be presented as well.
