I am an Indian national with a France Schengen visa valid until 2021. I know that a Croatia visa is not required if I have a multiple-entry Schengen visa. However, my old passport is full and I got a new passport. But I am not sure whether I can use the Schengen visa in the old passport together with my new passport to travel to Croatia. Could you please help me with this problem? Thanks.
Timatic, the database used by airport check-in staff, frequently outlines whether valid visas in expired passports (together with a new passport) are accepted by a given country, but there is no information on Croatia.
As such, without further information, you'will probably be denied boarding on a flight to Croatia.
For Slovenia and Hungary (Schengen countries), however:
Valid visas in full, invalidated travel documents are accepted if accompanied by a new travel document
So you could fly to one of those and catch the train or bus to Croatia from there. Croatian police at these borders is extremely relaxed towards EU/EFTA citizens, and fairly relaxed to others as well.
If you need to be 100% sure about Croatia, e-mail the police at firstname.lastname@example.org
Start the message by writing "To the border police department" and ask if valid Schengen visas in expired passports can be used together with a new passport.
They should give you a reply, although most likely in Croatian (Google Translate it in this case)