  We start a systematic investigation of possible isometries of the
asymptotically de Sitter solutions to Einstein equations. We reformulate the
Killing equation as conformal equations for the initial data at
$\mathcal{I}^+$. This allows for partial classification of possible symmetry
algebras. In particular, if they are not maximal, they may be at most
$4$-dimensional. We provide several examples. As a simple collorary it is shown
that the only spacetime in which the Killing horizon intersects $\mathcal{I}^+$
(after a conformal completion) is locally the de Sitter universe.
