  We study generalized global symmetries and their 't Hooft anomalies in 3d N=4
superconformal field theories (SCFTs). Following some general considerations,
we focus on good quiver gauge theories, comprised of balanced unitary nodes and
unbalanced unitary and special unitary nodes. While the global form of the
Higgs branch symmetry group may be determined from the UV Lagrangian, the
global form of Coulomb branch symmetry groups and associated mixed 't Hooft
anomalies are more subtle due to potential symmetry enhancement in the IR. We
describe how Coulomb branch symmetry groups and their mixed 't Hooft anomalies
can be deduced from the UV Lagrangian by studying center charges of various
types of monopole operators, providing a concrete and unambiguous way to
implement 't Hooft anomaly matching. The final expression for the symmetry
group and 't Hooft anomalies has a concise form that can be easily read off
from the quiver data, specifically from the positions of the unbalanced and
flavor nodes with respect to the positions of the balanced nodes. We provide
consistency checks by applying our method to compute symmetry groups of 3d N=4
theories corresponding to magnetic quivers of 4d Class S theories and 5d SCFTs.
We are able to match these results against the flavor symmetry groups of the 4d
and 5d theories computed using independent methods. Another strong consistency
check is provided by comparing symmetry groups and anomalies of two theories
related by 3d mirror symmetry.
