Home > Personal > Personal Lending > Mortgage > Mortgage Resources > Glossary > Underlying Mortgage Underlying Mortgage November 9, 2021 Generally refers to the first mortgage when there is a wraparound mortgage.You Might Also Like: Living QuartersSpring Maintenance Checklist for Your Home All Things CommunityHoli-days of Giving 2022 Everyday MoneyGiving Back During the Holiday Season Living QuartersYour Top Mortgage Questions Answered Living QuartersHow to Understand Mortgage Language