Co-borrower is an additional borrower on a loan whose credit and possibly income is used to qualify for approval of an application for a loan. Co-borrowers are equally responsible for repayment of the loan because their name appears on the promissory note. Co-borrowers are not required for all private student loans, but if the student has no credit history or poor credit history, the application may be declined. Co-borrowers with excellent credit may assist in obtaining a better rate on the private student loan.

If the primary borrower misses payments or defaults on the loan, the co-borrower is liable for the principal and interest. Because of that, they should make their decision to borrow carefully.