The polarizations of the $\ensuremath{\Upsilon}(1S)$, $\ensuremath{\Upsilon}(2S)$, and $\ensuremath{\Upsilon}(3S)$ mesons are measured in proton-proton collisions at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$, using a data sample of $\ensuremath{\Upsilon}(nS)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ decays collected by the CMS experiment, corresponding to an integrated luminosity of $4.9\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters ${\ensuremath{\lambda}}_{\ensuremath{\vartheta}}$, ${\ensuremath{\lambda}}_{\ensuremath{\varphi}}$, and ${\ensuremath{\lambda}}_{\ensuremath{\vartheta}\ensuremath{\varphi}}$, as well as the frame-invariant quantity $\stackrel{\texttildelow{}}{\ensuremath{\lambda}}$, are presented as a function of the $\ensuremath{\Upsilon}(nS)$ transverse momentum between 10 and 50 GeV, in the rapidity ranges $|y|<0.6$ and $0.6<|y|<1.2$. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region.