"This Old Dog" is a song by Mac DeMarco from his 2017 album of the same name. The track features a laid-back, mellow sound, characteristic of DeMarco's style, blending elements of indie rock and lo-fi music. The lyrics reflect themes of aging, nostalgia, and the complexities of relationships. The song showcases DeMarco's signature guitar work and soft vocals, creating an intimate atmosphere. It resonates with listeners through its relatable content and simple yet effective melodies, making it a standout piece in his discography. The overall vibe captures a sense of warmth and introspection.