I'd say yes.... but only just.
He was very much involved with the Impressionists, although today he seems to be pushed aside a bit, because he was working a little before them.
BUT, he was part of the famous 1863 Salon des Refusés exhibition, and this is the date many art historians use to mark the beginning of Modernism....
So I'd say yes, he can be regarded as a Modernist. Although some peoples views may differ.