Yes, TITIS is a Scrabble word!

Letter values in Scrabble US: T 1, I 1, T 1, I 1, S 1.

Is it a valid word?

TITIS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

tree of low-lying coastal areas of southeastern United States having glossy leaves and racemes of fragrant white flowers
deciduous shrubby tree of eastern North America having deeply fissured bark and sprays of small fragrant white flowers and sour-tasting leaves
small South American monkeys with long beautiful fur and long nonprehensile tail

Also: buckwheat tree, cliftonia monophylla, sorrel tree, oxydendrum arboreum, titi monkey.