McCombe this week had his contract at Vale Park terminated by mutual consent following almost five years with the Burslem club.
The 28-year-old centre-half leaves having played a key role in the Valiants' first promotion for 19 years, making 37 appearances as Micky Adams men finished third in League Two and sealed automatic promotion.
He told Mansfield's official website: "Hopefully we can kick on from the players' achievements last season and have another good year.
"I've had quite a bit of interest this summer [from other clubs] but after speaking to (Stags manager) Paul Cox and the rest of the staff, it seems like this club is heading in the right direction.
"I'm a centre-half who gives 100 per cent and I'll be giving everything now for Mansfield."
- Sports & Recreation