  Leptoquarks (LQs) are predicted within Grand Unified Theories and are well
motivated by the current flavor anomalies. In this article we investigate the
impact of scalar LQs on Higgs decays and oblique corrections as complementary
observables in the search for them. Taking into account all five LQ
representations under the Standard Model gauge group and including the most
general mixing among them, we calculate the effects in $h\to\gamma\gamma$,
$h\to gg$, $h \to Z \gamma$ and the Peskin-Takeuchi parameters $S$, $T$ and
$U$. We find that these observables depend on the same Lagrangian parameters,
leading to interesting correlations among them. While the current experimental
bounds only yield weak constraints on the model, these correlations can be used
to distinguish different LQ representations at future colliders (ILC, CLIC,
FCC-ee and FCC-hh), whose discovery potential we are going to discuss.
