The 62-year-old claims that Jose Mourinho is chasing the midfielder, who flourished under the Portuguese coach at Inter Milan.
"I know Chelsea and Jose Mourinho want Sneijder," van Gaal told Vatan.
"In my opinion, if possible Sneijder should leave Galatasaray and join Chelsea.
"Playing under Mourinho again would improve his performances and help him regain his form for the national team."
Sneijder moved to Turkey in January after being frozen out at the San Siro.