  We report on VLBI measurements of supernova 2014C at several epochs between
$t = 384$ and 1057 days after the explosion. SN 2014C was an unusual supernova
that initially had Type Ib optical spectrum, but after $t = 130$ d it developed
a Type IIn spectrum with prominent H$\alpha$ lines, suggesting the onset of
strong circumstellar interaction. Our first VLBI observation was at $t = 384$
d, and we find that the outer radius of SN 2014C was $(6.40 \pm 0.26) \times
10^{16}$ cm (for a distance of 15.1 Mpc), implying an average expansion
velocity of $19300 \pm 790$ \kms\ up to that time. At our last epoch, SN 2014C
was moderately resolved and shows an approximately circular outline but with an
enhancement of the brightness on the W side. The outer radius of the radio
emission at $t = 1057$ d is $(14.9 \pm 0.6) \times 10^{16}$ cm. We find that
the expansion between $t = 384$ and 1057 d is well described by a constant
velocity expansion with $v = 13600 \pm 650$ \kms. SN 2014C had clearly been
substantially decelerated by $t = 384$ d. Our measurements are compatible with
a scenario where the expanding shock impacted upon a shell of dense
circumstellar material during the first year, as suggested by the observations
at other wavelengths, but had progressed through the dense shell by the time of
the VLBI observations.
