Kane scored 41 times in all competitions for Tottenham Hotspur during the 2017-18 campaign, before netting six goals at the 2018 World Cup to claim the Golden Boot.
The player has also registered twice in four Premier League games for Spurs this season but looked laboured in England's matches with Spain and Switzerland.
The 25-year-old's early-season form at Tottenham has also been questioned despite his two goals, and Neville has said that the striker should have been given a rest during the September international break.
"I am concerned about Harry Kane. Since 2015 he has played 175 matches and he's struggling. Forget the physical side, he needs a mental break as well," Neville told Sky Sports News.
"I don't think he should have been here for the two weeks. I think there is a welfare thing in terms of looking after players. He has not had enough of a break since 2015."
Kane will be back in club action when Tottenham face Liverpool in the Premier League this weekend.