[10][11][12] In 2016, he played supporting roles in college romance series Cheese in the Trap and historical drama Moon Lovers: Scarlet Heart Ryeo.

[15] He then starred in his second lead role in the youth sports drama Weightlifting Fairy Kim Bok-joo alongside Lee Sung-kyung, portraying a talented yet playful swimmer named Jung Joon-hyung.

[16][17] In 2017, he led tvN's fantasy romance series The Bride of Habaek opposite Shin Se-kyung, wherein he portrayed a narcissistic Water God in pursuit of his rightful throne.

[20] Nam received acclaim for his performance, with Yoon Mi-sik of The Korea Herald writing that he "delivers a rock-solid portrayal of a wavering youth who is unsure of what is right or wrong."

[21][22] Nam starred in the fantasy romance drama The Light In Your Eyes alongside Han Ji-min and Kim Hye-ja in 2019, receiving positive reviews for his performance.

[30][31] He received favorable reviews for his performance in portraying the character Baek Yi-jin, with Korean media outlet OSEN referring to Nam as the "symbol of youth" as they commended his acting skills which created what is known as the "Joohyuk's Pain" syndrome.

Kim adds, "[Nam's] affectionate warm voice and clear gaze make viewers' hearts flutter and fall for Baek Yi-jin.

[37] On April 6, 2019, it was reported that Nam donated about ₩30 million to the Hope Bridge Association of the National Disaster Relief for the victims of the Gangwon Province wildfire in South Korea.

[38] In February 2020, he donated ₩50 million to the Daegu Social Welfare Community Chest to be used for quarantine supplies and medical support needed to prevent COVID-19.

On July 5, Korean news outlet Dispatch published an article containing statements of 20 people: 2 high school teachers and 18 classmates of Nam, defending him against the allegations.

[43][44][45][46] On March 28, 2024, the accuser of Nam has been found guilty of defamation and ordered to pay 7 million won in restitution to the actor by the Goyang District Court.