Kim Shin (Gong Yoo) is a goblin and protector of souls. He is the landlord of the grim reaper (Lee Dong-wook) who is in charge of taking deceased souls. Shin doesn't want immortality anymore but needs a human bride in order to end his long life. Meanwhile, Ji Eun-tak (Kim Go-eun) is a high school student who despite her painful reality, remains optimistic. She summons the goblin by chance and through various encounters, ends up falling in love with him. Sunny (Yoo In-na) is an owner of a chicken wing shop, a woman who is loved by all men and is also the reincarnation of the goblin's sister. These four people's lives change when they encounter and their lives become entangled.
A 939-year-old immortal goblin and protector of souls who is in search for his bride, the only one who can remove the sword piercing through his chest. Once the sword is removed, he may finally move to the afterlife and rest in peace. He possesses supernatural powers that come with his immortality but he has to pay a huge price for this. He feels lonely as he has to watch his loved ones leaving him behind when their lifespan ends.
A good-looking, cynical yet humorous character grim reaper (grim reapers receive their jobs as a punishment for committing the greatest of sins in their past lives) who guides souls to their reincarnations or afterlives. Along with the other grim reapers, he has no memory of his past lives. He has a strong friendship with the Goblin.
The attractive owner of a chicken restaurant who falls in love with the Grim Reaper. She is constantly confused by the Grim Reaper's constant social awkwardness, but is intrigued by him otherwise. She is also the young sister of Kim Shin.
A rebellious yet kind-hearted chaebol heir and the only grandson of the Yoo family, a household that has the responsibility of taking care of the Goblin. Living with the Goblin and the Grim Reaper, Deok-hwa learns of their true identities, and the trio grow to be strong friends.
There was a controversy surrounding the release of the song “Round and Round”. Originally, the song was sung by Han Soo-ji. However, when the song was officially released, Han was merely a featuring on the track, which was sung by Heize. This caused dissatisfaction among fans, who loved Han's voice. CJ E&M released an official apology, saying that Han was enlisted to record just the first 50 seconds of the song, but the writer of the song, Nam Hye-seung, requested since the beginning that the full song be sung by another vocalist.
The drama was a hit and consistently topped cable television viewership ratings in its timeslot. Its final episode recorded an 18.680% nationwide audience share according to Nielsen paid platform, making the episode the second highest rated in Korean cable television history. It became the first cable drama to surpass 20% ratings. It was also popular among the international audience, which led to parodies of the drama on various social media sites, notably by both celebrities and political figures.
The drama has also sparked various fashion trends. Items and accessories worn by the cast members, such as the Lavin coat worn by Gong Yoo, Lancôme lipstick used by Kim Go-eun and Fedora worn by Lee Dong-wook saw an increase in sales. Kim In-yook's poetry book, The Physics of Love, gained renewed attention after one of its verses was featured in the drama. There was also an increase in visitors at the various filming sites of Guardian, which contributed to a positive economic effect on the country. Additionally, original soundtracks featured in the series also topped local digital music charts. Since 2017, it has surpassed Descendants of the Sun (2016) in video-on-demand sales.
Its success was attributed to the creative plot.The Korea Times stated, "...the depth of perspective looking at life of the goblin that bears a bloody sword in his chest and has been given eternal life as punishment, immerses the audience into the fantasy story. The twist and complexity of life and death make the story more interesting."
Despite its success, Guardian was criticized for its several consumer product placements (as well as Kim Eun-sook's previous hit-drama Descendants of the Sun in 2016) which drew an estimated 2-4 billion KRW from revenue. TV and cultural critics also criticized various aspects of the drama, such as its strong emphasis on Cinderella complex and the huge age gap of the lead characters, which might lead to a decline in female's social status. It was also criticized for its over-dramatic plot.
In Brunei, Hong Kong, Indonesia, Malaysia and Singapore, the drama aired on Oh!K with subtitles. It was retitled as "Goblin" in promotional materials and during broadcast. It premiered on December 3, 2016 24 hours after its original broadcast in South Korea.
In Sri Lanka, Brunei, Malaysia, the Maldives and Vietnam, the drama is available to stream on-demand on Iflix. It was retitled as "Goblin" in promotional materials. During its original run, episodes of the drama were exclusively streamed on Iflix within 24 hours of its original South Korean broadcast with subtitles between December 3, 2016 and January 22, 2017.