Diboson and EWK Physics at CMS

We present the most recent studies of diboson production and electroweak physics in proton-proton collisions at 7 TeV and 8 TeV center-of-mass energy based on data recorded by the CMS detector at the LHC in 2011 and 2012. These include precise measurements of $\gamma\gamma$, ZZ and WZ production. Results on triboson production of WW$\gamma$ and WZ$\gamma$ are also presented. The results are interpreted in terms of constraints on anomalous triple or quartic gauge couplings. We also review some recent electroweak physics results, including the purely electroweak Z bosons production cross section and the muon charge asymmetry measurement. The results are compared with Standard Model prediction.