Second 20s^[1] (Korean: 두번째 스무살; RR: Dubeonjjae Seumusal; lit. Twenty Years Old for the Second Time) is a 2015 South Korean television series starring Choi Ji-woo, Lee Sang-yoon, Choi Won-young, Son Na-eun and Kim Min-jae.^{[2][3][4][5][6][7][8]} It aired on tvN from August 28 to October 17, 2015, on Fridays and Saturdays at 20:30 (KST) for 16 episodes.^[9][10][11]

Ha No-ra once dreamed of becoming a dancer, but she unexpectedly became pregnant at age 19 and had to quit school and get married. For the next two decades, her life revolved around being a housewife and mother. Now 38 years old and on the brink of divorce, No-ra is diagnosed with terminal pancreatic cancer and given a six-month prognosis. So she decides to go back to school and experience college life for the first time.^[12] Among the incoming freshmen are her own 20-year-old son Kim Min-soo and his girlfriend Oh Hye-mi, who are horrified to have No-ra as their classmate.^[13] Unbeknownst to No-ra, her intellectual snob husband Kim Woo-chul recently accepted a job teaching psychology at the same university, and her prickly theater arts professor turns out to be Cha Hyun-seok, who had a crush on No-ra in high school.

• Choi Ji-woo as Ha No-ra
  • Ha Seung-ri as young No-ra
• Lee Sang-yoon as Cha Hyun-seok
  • Kim Hee-chan as young Hyun-seok
• Choi Won-young as Kim Woo-chul
  • Kang Tae-oh as young Woo-chul
• Son Na-eun as Oh Hye-mi
• Kim Min-jae as Kim Min-soo
• Han Sung-yun as Hyun-Jung
• Jung Soo-young as Ra Yoon-young
  • Im Ji-hyun as young Yoon-young
• Noh Young-hak as Na Soon-nam
• Woo Ki-hoon as Woo-hun
• Choi Yoon-so as Shin Sang-ye
• Ji Ha-yoon as Min-ae
• Jin Ki-joo as Park Seung-hyun
• Kim Kang-hyun as Seo Dong-chul
• Ban Hyo-jung as Seo Woon-hae, No-ra's grandmother (cameo)

In this table, the blue numbers represent the lowest ratings and the red numbers represent the highest ratings.

• This drama airs on cable channel/pay TV which has a relatively small audience compared to free-to-air TV/public broadcasters (KBS, SBS, MBC and EBS).