The 32-year-old was given time off by West Ham in the wake of Russia's invasion of Ukraine this week.
"I said before that I think Premier League football is looked to throughout the world," said Moyes.
"Wherever you are in the world, Premier League football is watched, whatever continent you are [on].
"It was a brilliant message that they are putting out all round, saying nobody over here, nobody in this part of the world, is recognising war. We don't want to. We don't want to hear about.
"We support Ukraine and we want to try and support our player in Yarmolenko. At the moment, we have given him a bit of time off.
"I am hoping and I believe he is going to come back into training tomorrow. But we are really just more interested that he has got his family safe and everybody connected with himself is okay."